After comprehensive testing, here’s iRunFar’s guide to the best hydration packs for running.

When you need to carry water, snacks, and clothing on a run, choose from among the best hydration packs available. PP Plastic Panel

Running has long been considered a simple sport — just lace up your shoes and hit the trail, right? This blissfully simple strategy works great for a few miles, but what happens when the minutes turn to hours — or days, in some cases? From food to hydration, phone to first aid, layers to trekking poles, the longer the run, the more stuff is involved to make it a safe and happy experience.

When you are in it for the long haul, you need a comfortable way to carry that pile of gear. The running hydration pack, also referred to as a running vest, is a vital accessory when chasing long days on the trails or packing a list of mandatory race equipment.

Lucky for us, an enormous amount of innovation has happened on the running vest front. Gone are the days of rigging up a backpack to not bounce too much, and here to stay is a dizzyingly extensive list of running hydration pack options. These choices are great, but they can make shopping for a running hydration pack downright exhausting.

To help you save that energy for your next long trail run, the iRunFar team spent the summer loading up and hitting the trails to determine which running vests rise to the top of this enormous pile. From quick aid station refills to comfortably carrying gear for all-day affairs, we break down the best running vests available on the market today.

For more background information about the best hydration packs for trail running, see our buying advice, testing methodology, and frequently asked questions below the picks.

Use these links to skip directly to the pack you’d like to learn more about:

Best Small-Capacity (1 to 5 Liters) Hydration Packs 

Best Medium-Capacity (6 to 11 Liters) Hydration Packs

Best Large-Capacity (12 to 15 Liters) Hydration Packs

Maggie Guterl tests an UltrAspire hydration pack outside of Durango, Colorado. Photo: iRunFar/Eszter Horanyi

Any search for the best trail-running hydration pack will lead to multiple mentions of Salomon packs, and after months of testing, our testers wholeheartedly agree that options from this brand have earned their place at the top of the pile. The Salomon Adv Skin 5 unisex running vest and Salomon Adv Skin 5 women’s running vest are no exception and were a nearly unanimous choice for our best low-volume pack.

This five-liter pack features two pockets on the front that fit 500-milliliter soft flasks, each with an additional stretchy pocket overlying it and a smaller zip compartment on one side. The flasks sit high on the chest in the unisex version of the pack and are easy to drink out of without having to remove the flask from its pocket. An elastic loop secures the top of the flask so that it doesn’t fall into the pocket as it empties.

The additional front pockets can fit plenty of smaller items like gloves, a buff, gels or chews, or lip balm, and they can also fit most cellphones for quick access. The rear has one large compartment with a separate hydration bladder sleeve, which can fit a 1.5-liter bladder. This compartment includes a panel to protect your gear from moisture from sweat or the hydration bladder, though some testers found that this extra layer of fabric increased heat retention on their back during hot weather runs.

Across the lower back is another pass-through stretch sleeve to stash a jacket, hat, or smaller gear in an accessible place. Salomon’s Sensifit construction includes well-placed stretch panels so that your pack can fit an impressive amount of gear comfortably and securely without it shifting, bouncing, or feeling too compressive. This pack easily fits the same amount of gear, or potentially more, than many of the higher-capacity packs we tested, and I have used it for multiple supported ultramarathons and six-plus hour training runs in the forests of New England with ease.

An elastic sternum strap has multiple attachment points to personalize fit and make adjustments on the fly easy with a single pull-through toggle to tighten and loosen it. Multiple trekking pole-carrying configurations are possible with the attached elastic cords on the front and back, or with Salomon’s separate quiver. An attached whistle on the front of the pack and a key clip in the rear compartment are small but very helpful details.

The Salomon Adv Skin 5 is available in a unisex fit as well as a women’s-specific version. The women’s fit has a similar pocket setup but positions the soft flask pockets lower to avoid pressure over the chest and uses a longer drinking straw. This does change the fit and feel of the pack significantly, and the best fit for any individual really just comes down to personal preference. Most of our female testers preferred Salomon’s unisex pack, but runners with larger chests may appreciate the women’s fit.

To learn more, read our in-depth Salomon Adv Skin 5 review.

Hydration Carrying Method: Two 500-milliliter flasks (included) in front sleeves, 1.5-liter bladder (sold separately) in rear

Gender-Specific or Unisex Sizing: Unisex and women’s-specific model

Shop the Salomon Adv Skin 5 Unisex Running Vest Shop the Salomon Adv Skin 5 Women’s Running vest

The Osprey Duro 1.5 and the Osprey Dyna 1.5, the women’s version of the pack, are 1.5-liter low-volume race-ready packs that have everything you need for short and fast days on the trail. A rear zip compartment fits the included 1.5-liter hydration reservoir and two large front stretch pockets that can fit nutrition, small gear, or Osprey’s 500-milliliter or 360-milliliter soft flasks, which are sold separately, allow for expanded hydration capacity. Our testers noted that the rear pocket cannot fit additional gear if the hydration bladder is being used, but there is an exterior bungee cinch cord to carry a jacket or extra layer. A smaller front zip pocket and two stretch pockets under the arms for small items like a buff, hat, or gloves round out the storage capacity. The rear hydration bladder compartment has a diagonal zipper opening, which only allows the tubing to route over the right shoulder, something to keep in mind if you prefer it on the left.

The sternum strap is secured with plastic snaps that clip on each of the shoulder straps rather than having a center buckle, making it easy to adjust their positioning to your comfort. Our testers found this pack to run a little on the small side in the arm holes, so if you have broader arms or shoulders, you may need to size up. The material is a little thicker and heavier than that of some of the other tested packs but is very durable while still maintaining breathability.

As with our other winning picks, this pack includes a trekking pole-attachment system and a safety whistle on the front. For a small-capacity pack, we found it to include a lot of thoughtful details and a hydration capacity on par with many larger packs.

If you love the fit and function of this pack but are looking for something with more gear storage capacity, Osprey offers a 6-liter version of the Duro and Dyna as well that you can learn more about in our Osprey Dyna 6/Duro 6 review.

Hydration Carrying Method: 1.5-liter hydration bladder (included), can fit two 360-milliliter or 500-milliliter soft flasks in front pockets (sold separately)

Gender-Specific or Unisex Sizing: Gender-specific, Duro (men’s) and Dyna (women’s)

Shop the Osprey Duro 1.5 Shop the Osprey Dyna 1.5

The Nathan Pinnacle 4 Liter Hydration Race Vest and the Nathan Pinnacle 4 Liter Women’s Hydration Race Vest are breathable, lightweight running vests that provide easy access to hydration and gear for shorter trail runs and well-supported ultra runs alike. This hydration vest features a familiar front pocket setup with two larger stretchy sleeves to fit the included 500-milliliter flasks. These flasks feature extended drinking straws and a firm piece of plastic built in to help them maintain their shape and keep them from sinking into the pocket when empty. The straws stayed in place for our testers with no annoying flopping. The front storage also includes a water-resistant zipper pocket on each side that can fit most cellphones. The pocket is tucked behind the flask pocket, which our testers found worked well but put increased pressure on the ribs with a phone in the pocket and a full soft flask.

Stretchy rear compartments can fit a 1.5-liter bladder, and there is also a vertical trekking pole pocket that our testers found worked well with no bounce. Small stretch pockets over the front flask sleeves, stretch compartments under the arms, and two kangaroo pockets across the lower back provide additional storage for all of your long-run or race-day needs.

The hydration pack features a similar but lighter-weight fabric to its predecessor, the VaporKrar and VaporHowe line, and also has a modified shape with a longer back to help disperse gear. Our testers found the fabric soft and comfortable against the body. The nylon sternum straps feature standard buckle closure and a sliding rail to easily adjust their position up and down the front of the pack. This pack comes in unisex and women’s-specific sizing, and we found it to run on the larger side — a measurement-based sizing guide on Nathan’s website is helpful to determine the correct size for you. This vest also comes in a larger 12-liter size for those who like the fit and style of the pack but need more storage capacity for longer adventures.

Liquid Capacity: 2.8 liters (can fit a standard 1.5-liter bladder or Nathan’s 1.6-liter or 1.8-liter hourglass-shaped bladders)

Hydration Carrying Method: Two 500-milliliter front flasks with straws (included), rear hydration bladder up to 1.8 liters (sold separately)

Gender-Specific or Unisex Sizing: Unisex and women’s-specific available

Shop the Nathan Pinnacle 4 Liter Hydration Race Vest Shop the Nathan Pinnacle 4 Liter Women’s Hydration Race Vest

Mid-volume packs bridge the gap between wanting to carry the bare minimum but not quite needing the capacity for a full-day unsupported journey. These packs are a great size for a 3-plus hour run or a supported ultramarathon where you may need to go a few hours between aid stations but don’t need to carry your whole day’s nutrition and water. The UltrAspire Alpha 5.0 Race Vest has a six-liter capacity and some thoughtful features that made it our tester’s top pick in this category.

UltrAspire’s ErgoFit harness design has curved and angled shoulder straps and lowers the center of gravity of the pack to reduce fatigue on the neck, improve weight distribution and stability, and enhance the arm’s range of motion. Our smaller testers found that this pack initially felt large and a little loose but stayed stable with no bounce even if the front elastic straps were not tight. This allowed for good chest expansion when breathing and eliminated that overly compressed tight feeling that is common with many other packs.

The front of the pack has two large pockets that can fit quickly needed items like food and gels and can also hold a pair of 500-milliliter soft flasks or UltrAspire’s flexible hybrid bottles. These pockets are oriented lower on the chest so the bottle or flask needs to be removed when drinking, but they are nice and wide to make reinserting the bottle easy. Zippered side pockets under the arms were a favorite feature of ours, keeping items secure but easy to reach.

The rear compartment spans the length of the pack providing extra storage capacity and fits the included two-liter hydration bladder in a separate sleeve that has a removable Mylar-insulated insert to maintain your liquids’ temperature. A magnetic-closure pass-through pocket and elastic cinch cord provide additional quick-access rear storage for an extra layer or extra snack. Elastic shock cord loops on the bottom of the pack are the only trekking pole attachments, and we found these to be a bit bouncy and not as stable as other packs.

The hydration pack has a lightweight honeycomb mesh next to the body that wicks moisture well, but the other materials of the vest are thicker when compared with other similar packs. This may improve long-term durability but makes the pack heavier. This pack has a longer profile, especially in the back, and may feel long on more petite runners or those with a shorter torso.

The elastic cinch-cord sternum closure is fixed in place but quite comfortable with a simple-to-use hook — no fumbling around a complicated buckle with tired or cold fingers. A small magnetic-closure water-resistant pocket is perfect for pills or salt tabs, and a stretchy sleeve with a cinch closure on the left shoulder is made for a cellphone.

My iPhone 12 Pro fit, much to my surprise. This pocket is also a good place to stash a gel or chews if you prefer more secure phone storage. For those of us who hate bouncing cords, the front left pocket has a small pass-through to tuck the end of the shock cord away once it is secured and tightened, which is a nice touch. As one of our testers succinctly put it, “UltrAspire nails the little things.”

Hydration Carrying Method: 2-liter hydration bladder (included), can fit two 500-milliliter flasks or UltrAspire bottles in front pockets (sold separately)

Gender-Specific or Unisex Sizing: Unisex

The Swedish company USWE (pronounced “you-swii”) has its origins in the off-road motorcycle and bicycle world, with a fairly recent foray into running hydration packs. Their innovation led to the creation of the USWE Pace 8L Trail Running Vest, one of our top picks in the mid-volume pack category.

This 8-liter pack features USWE’s signature “No Dancing Monkey” harness system that provides a secure fit with no bounce. The front closure system is unique, with one large circular buckle that our testers praised for its simplicity and ease of use. The pack’s adjustment points are elastic draw cords on the sides that cinch to tighten the fit while still allowing some expansion with breathing and movement. The material is very lightweight and stretchy, comfortable when on, and expandable to accommodate gear. A bonus is their polygiene material treatment, which is supposed to prevent odor and improve the longevity of the pack.

Two front pockets carry the included 500-milliliter soft flasks. These are oriented lower on the body and have attached drinking straws to allow for sipping on the go without having to remove the flask. The flasks have rather small openings, which we found to be inconvenient for refilling, especially if using an electrolyte powder or drink mix. Two stretch pockets over the flask pockets are nicely expandable and can fit a cellphone, gels, and other smaller items.

The rear compartment can fit a two-liter bladder (not included) and utilizes two pull-tight straps on the shoulders to compress the bladder, securing it and preventing movement and bouncing. There are two additional pockets across the lower rear of the pack, both with zipper closures to keep items secure. These overlie each other and can be difficult to reach with the pack on, making them less convenient than an open-ended kangaroo-style pocket. One of these compartments has a zipper opening on the bottom, which could lead to gear falling out if it is not fully zipped. The cinch system eliminates pocket space under the arms, reducing storage capacity there.

The trekking pole attachment sits diagonally across the front of the pack, which can interfere with the storage pockets and may not be comfortable for runners with narrow builds or larger chests.

If you like the fit and design of the USWE Pace 8L Trail Running Vest but are looking for a lower capacity race-ready vest, USWE also makes a two-liter version that has the same design and fit but eliminates the larger rear pocket — you can check out our USWE Pace 2 Running Vest review.

Hydration Carrying Method: Two 500-milliliter straw soft flasks (included), can fit a 2-liter bladder (sold separately) in the rear

Gender-Specific or Unisex Sizing: Unisex

CamelBak has long been a household name in the hydration pack game, and the CamelBak Ultra Pro Vest 34 Ounce and CamelBak Women’s Ultra Pro Vest 34 Ounce is a solid offering in their running-specific line that packs a lot of handy pocket space and features into a compact six-liter package — perfect for race day. There are two pocket options on the front to hold the included 500-milliliter Quick Stow flasks, with extra pockets over these, including a zippered pocket with an extra inner pouch that is great for a key or money. Mesh stretch pockets under the arms, a rear pass-through pocket, and one large main compartment that can hold up to a 1.5-liter bladder complete this pack’s pocket setup. The pack is lined with a soft lightweight perforated mesh that breathes well and is comfortable against bare skin, and the outer materials are a nice combination of lightweight stretchy mesh and durable nylon.

Two adjustable sternum straps attach with simple buckles that we found very easy to use. There are two bungee attachments on the back for trekking poles, holding them vertically along the length of the pack. The large rear compartment has a fabric loop and tiny attached plastic clip to secure it closed. This is tricky to attach and not very user-friendly, and our testers found it essentially unusable on trail, but we had no issues with gear staying put in the pocket without using this closure.

The hydration pack comes in two gender-specific models, which have slightly different pocket and flask arrangements. The flasks sit higher on the chest in the women’s version, and the men’s has lower flask sleeves and two smaller pockets higher on the shoulder straps above the flasks.

The nylon rear material trapped heat more than some other running vests, which may be an issue for runners in hot climates. Some of our testers found the CamelBak flasks more difficult to drink out of than other similar flasks, though this did get a little better with more use.

Hydration Carrying Method: Two 500-milliliter front flasks (included), can fit a 1.5-liter bladder (sold separately)

Gender-Specific or Unisex Sizing: Gender-specific, with a different front layout for men’s and women’s version

Shop the CamelBak Ultra Pro Vest 34 Ounce Shop the CamelBak Women’s Ultra Pro Vest 34 Ounce

If you look around the starting line of most any ultramarathon, you will see many runners wearing the Salomon Adv Skin 12 unisex running vest and Salomon Adv Skin 12 women’s running vest, and for good reason! This 12-liter vest was our tester’s hands-down favorite in the high-volume pack category and has topped the list of many other hydration pack reviews. This pack is essentially a bigger version of the Salomon Adv Skin 5 hydration packs reviewed above, with some modifications that make it the perfect pack for long days on the trail and self-supported adventures where you’ll be carrying your gear and nutrition for the entire day.

This pack features the same stretchy materials, elastic cord chest straps, mesh lining, and Sensifit construction as the five-liter version, so it can haul a serious amount of gear while maintaining a snug vest-like fit. The front pocket setup is also similar to the smaller version, with sleeves for two included 500-milliliter soft flasks, large stretch stuff pockets, and two zipper compartments to keep small items or your cellphone secure. Our testers found the flasks were a little tricky to get back into their sleeves on the unisex version as compared with some of the other packs with wider flask pockets.

The rear features the hydration bladder pocket which comes with a thermal sleeve to maintain your water’s temperature in hot or cold weather. The large rear main compartment is accessed by a vertical side zipper and has some impressive stretch to fit all the gear you need for a full day of running. Bungee compression cords on either side of the back help to stabilize the load. A smaller stuff pocket at the top of the rear can fit an emergency blanket or small jacket, and the pass-through tunnel pocket across the lower rear provides additional storage that is easily accessed on the go.

This pack has the unique ability to wear equally well when it is loaded up as when it is empty, making it a popular choice for ultra runners who like to carry hydration and nutrition for both shorter training runs and long efforts but don’t want to invest in a closet full of packs. There are multiple attachment options for carrying trekking poles on the front and rear, and there is also a separate quiver that can be attached. This pack is available in a unisex and a women’s version, which has lower flask pockets and straw flasks that sit below the chest.

Hydration Carrying Method: Two 500-milliliter soft flasks (included), 1.5-liter hydration bladder (sold separately)

Gender-Specific or Unisex Sizing: Unisex and women’s-specific fit

Shop the Salomon Adv Skin 12 Unisex Running Vest Shop the Salomon Adv Skin 12 Women’s Running vest

The UltrAspire Zygos 5.0 Hydration Pack is a well-built 14-liter hydration pack made for fully loaded all-day adventures. As with the UltrAspire Alpha 5.0 Race Vest reviewed above, this pack also features the ErgoFit harness design to enhance fit, stability, and comfort. The liner material of the pack features a soft mesh combined with thicker padded material at pressure points on the back and chest to optimize breathability and comfort. The pockets are a combination of reinforced nylon and Dyneema fabric, making them durable yet stretchy for comfort and increased storage capacity.

The front of the vest has large stretch pockets that can fit 500-milliliter soft flasks or UltrAspire’s hybrid bottles, as well as additional zip and stretch compartments for food, maps, a cellphone, and any other smaller gear you want to have close at hand. Our testers found that these pockets are a bit loose, which led to some bouncing and shifting of small items if they are the only thing in the front pocket.

The side underarm pockets are large and stretchy, perfect for stashing gloves or a buff. One has a zip closure and one a magnet closure to keep gear more secure. The rear has a bladder sleeve with a removable insulated insert that holds the included two-liter hydration reservoir. A large zip pocket spans the back of the pack and has a nice wide opening for gear access. It also has an inner small zip compartment that has an attached key clip and an external stretch stuff pouch to quickly stash an extra layer. There are two draw cords across the back to cinch down and compress the pack when loaded with water and gear, which can also be used to quickly stow a jacket. The materials are thick and durable, but this, along with the black color, retained heat, and we found this pack to run warm — but not intolerably so.

The UltrAspire Zygos 5.0 Hydration Packs’ only fit adjustment point is the front shock-cord setup, billed as the MaxO2 Form adjustable closure system. Elastic cords join together with two clips across the chest and the closure is then tightened by pulling downward on the excess cord through a bungee locking mechanism. This pulls the cord tight, cinching the pack down across the chest.

This is easily undone by loosening the two bungee clips on either side to let out a little of the cord. Rear bungee loops across the low back of the pack hold trekking poles horizontally in place. We found this pack to be a little heavier than others but very sturdy and a great workhorse of a pack for long trail and mountain days.

Hydration Carrying Method: 2-liter bladder (included), can fit two 500-milliliter soft flasks or UltrAspire hybrid bottles (not included)

Gender-Specific or Unisex Sizing: Unisex

The Ultimate Direction Mountain Vest 5.0 and the Ultimate Direction Mountain Vesta 5.0, the women’s version of the pack, are great options in the high-volume pack category. This hydration pack has a stated 13.4-liter capacity for the men’s version and 12.7 liters for the women’s version. There is quite a bit of overlap between the men’s and women’s size ranges, which makes this capacity difference a bit confusing. The pack’s lining is a lightweight nylon mesh that wicks moisture well but is not as soft against the skin as some of the other packs we tested. The pocket material is a mix of nylon panels with some stretchy areas to improve gear capacity and fit.

The front of the pack has two stretch pockets that fit the included 500-milliliter soft flasks with a bungee cinch closure on the top to keep them in place. The flasks do tend to sink into their pockets as they empty. There are some additional front stretchy pockets that can fit some nutrition and smaller items but are sewn down the center to create two compartments, making them less functional than perhaps they could be.

Two lower pockets wrap toward the ribs, one with a zipper closure that fit my regular-sized iPhone more comfortably than expected. Two additional smaller pockets on the shoulders have Velcro closures and have a tunnel behind them to route the hydration bladder tubing through. The rear storage is ample and well-balanced with a large compartment with a clamshell-like zipper opening. A stretchy stuff pocket overlies this and is perfect for an easy-access jacket. A bungee cinch cord can be used to hold an additional layer and attaches to small hooks along the edges of the pack to provide compression when the pack is loaded with gear.

The pack has two adjustment points to dial in fit. The two sternum straps attach with simple plastic buckles that slide on a rail to quickly and easily adjust their position on the chest. The rear has Ultimate Direction’s Comfort Cinch 2.0 adjustment system, a cinch cord that pulls the lower part of the vest inward to tighten the fit. We found this system adjusts fit well but can take some practice to get comfortable using it as it requires reaching behind your back to tighten and loosen the cord. The front trekking pole holders are secured and use a snap to avoid unnecessary bouncing cords when not in use, which is a much-appreciated touch. Overall, this pack has a nice balance of lightweight materials, extra features, and gear capacity.

Gear Capacity: 13.4 liters (men’s), 12.7 liters (women’s)

Hydration Carrying Method: Two 500-milliliter soft flasks (included), up to 2-liter hydration bladder (sold separately)

Gender-Specific or Unisex Sizing: Gender-specific

Shop the Ultimate Direction Mountain Vest 5.0 Shop the Ultimate Direction Mountain Vesta 5.0

The UltrAspire Spry 3.0 Race Vest is a 3.5-liter capacity pack that offers great storage and features in a very affordable package. The materials are breathable and lightweight with just enough pockets to hold your essentials for anything from a half marathon to a fast, well-supported ultra run. In addition to being our budget pick, this vest rated very highly overall in the low-volume testing category as well.

Two front pockets are oriented lower on the chest and can hold hydration in a soft flask or the UltrAspire Ultraflask 550 hybrid bottles, or they can be used for quick access to small gear and nutrition. Our testers didn’t love that the flasks needed to be removed to drink but otherwise liked the front pocket arrangement. A single rear pocket can fit a one-liter bladder and includes a sweatproof liner, a smaller water-resistant zipper pocket, and magnetic closure. An external elastic shock cord on the back can be used to stash a jacket.

This vest utilizes the same ErgoFit harness with its elastic chest strap and hook closure as the above-reviewed UltrAspire Alpha 5.0 Race Vest, with simple webbing straps on the sides to adjust fit. This pack is unique in that it is one size fits most. According to UltrAspire’s size chart, it can fit a chest size range from 26 to 48 inches, accommodating a wide array of body types. There are no flasks or hydration bladder included, so this will add an additional cost if you want them. Even with that extra cost, this vest is still more affordable than most similar setups on the market.

Hydration Carrying Method: Can fit two 500-milliliter flasks or hybrid bottles in the front and a 1-liter bladder in the rear pocket; no flasks or bladder are included in the vest purchase

Gender-Specific or Unisex Sizing: Unisex, one size fits most

At first glance the Kailas Fuga Air II Trail Running Hydration Vest Pack 5L looks similar to many of the other low- to mid-range packs on the market, but this pack has a few unique design elements that set it apart from the rest.

The pack’s materials are lightweight and breathable with just enough stretch in the pockets to expand for gear storage while still keeping things secure. Our testers found the mesh honeycomb lining very breathable in hot and humid weather. The front features the standard stretch soft flask pockets which fit the included 500-milliliter soft flasks. The flasks themselves have a short angled drinking nozzle that rotates, which makes drinking on the move easy with less craning of your neck to reach the mouthpiece. Additional stretch pockets add storage for small things like nutrition.

On the front left there is a dedicated cellphone pocket, which zips along the side to allow easy access, and a tunnel underneath the flask pocket tucks in the top of the phone, keeping it secure and flat against the chest. The zipper makes it easy to slide the phone in and out for nature photos or music adjustments, even with a full flask in the upper pocket. The rear of the pack has a familiar layout with one large stuff pocket on the top and another across the low back.

The lower pocket is only accessible from the top rather than having the kangaroo-style bottom access offered by some of the other packs tested. We found this style of pocket to be more difficult to access while wearing the pack. A zipper pocket sits against the low back inside the lower stuff pocket. The pack does not have a sleeve or clip for a hydration bladder and is designed to use the front flasks only. If you are looking for more hydration and storage capacity, Kailas also offers an eight-liter version of the pack with more rear storage and a compartment for a hydration bladder.

The chest closure on this pack is a cord system with three plastic clips that attach to fixed points on the shoulder straps. These are adjusted with a Boa-like system that Kailas calls its ADF or “All-round Dial Fit” adjustment system. It cinches the cord system tight across the chest for a secure fit. Turning the knob clockwise tightens the cords and pulling out on the knob loosens them.

Our testers liked the innovative strap system but found that pulling out on the knob loosens the cords significantly, with no option for more precise adjustments of the fit. The cords are not stretchy and can compress the chest if over-tightened, so finding the best fit can take a little trial and error. The cords can also twist and tangle some when the pack is off, which makes taking the pack on and off during use on trail or in a race inconvenient.

There are multiple attachment options for trekking poles on the front and back of the pack using elastic cinch cords. The pockets where the cords are located all have small reinforced pass-through openings so they can be tucked away when not in use to eliminate annoying flopping and bouncing without having to remove the cords completely, a small detail we appreciated. An attached whistle and key clip tucked into the front pockets complete the list of small but helpful accessories.

Hydration Carrying Method: Two 500-milliliter soft flasks (included)

Gender-Specific or Unisex Sizing: Unisex

Shop the Kailas Fuga Air II Trail Running Hydration Vest Pack 5L

One of the main delineating features of the best running vests is the size of the pack. The pack capacity is typically described in liters, much like a hiking or backpacking pack is. Running hydration packs are much smaller than a traditional backpack and are designed to be form-fitting and more vest-like to eliminate bounce. The storage capacity of running packs is usually broken up into multiple pockets and compartments, usually split between the back and the front chest area rather than having one large rear pocket like a traditional backpack.

While there are a lot of variables that go into choosing the best pack for you, a good rule of thumb is to choose a pack size based on the amount of time you will be out on the trails. For shorter runs of less than two hours, or a race with frequent access to aid stations, a smaller capacity pack of two to five liters will be adequate to carry your hydration, food, and essentials. For those mid-range runs that are in the three- to six-hour range, or in more challenging or slow-going terrain, one of the midsize six- to 11-liter packs will give you a little extra storage space for gear and liquid carrying capacity.

For all-day adventures or runs in more mountainous terrain where extra gear and layers will be required, a larger pack in the 12- to 15-liter range will be needed. If you are considering a race with a mandatory kit, this larger capacity is the best choice for stowing your rain jacket, layers, headlamp, and other essentials. Running-specific hydration packs max out in the 15-liter capacity range. If you are looking for a larger capacity pack for a longer or multi-day adventure, check out our best fastpacks guide, as these will better serve the needs of that type of run or hike.

Once you decide on the right capacity, the most important consideration when choosing your running pack is the fit. Running hydration packs are close fitting, with a vest-like wraparound style that sits higher on your torso than a traditional backpack. This fit makes it easier to access storage on the go and keeps it close to your body to reduce bouncing and shifting with your running gait and arm swing.

Most running vests are made of material that have some give to move with you while you are twisting, running, or breathing. They typically have at least one point of adjustment, most often an adjustable chest strap to tighten and loosen the pack easily on the fly. The straps can allow for the addition and removal of gear and hydration without compromising the fit of the pack.

Some running vests have additional areas of adjustment on the sides or back of the pack and on the shoulders to help distribute weight for comfort and eliminate bouncing and shifting of your gear when loaded up for a long run. These can range anywhere from a simple strap to a more complicated webbing or Boa adjustment system to really dial in fit.

In an ideal world, we can try on a pack in a store before buying, but depending on where you live and which company you are shopping, this is often not a feasible option and many of us are shopping for our running vests online. All hydration pack manufacturers have different sizing and fits, so it is important to review their brand-specific measurement and fit guides to be sure you are selecting the right size and fit for you. Some people like their packs super snug while others want a little breathing room, so this will be subjective based on your needs. The most important measurements for pack fitting are around the widest part of your chest and around the bottom of your ribcage.

Maggie Guterl tests phone storage on the CamelBak Women’s Ultra Pro Vest 34 Ounce, which we named a top hydration pack for trail running. Photo: iRunFar/Eszter Horanyi

When trying a pack on for the first time, you’ll find that you can get the best fit if you load a long run’s worth of essentials — or some volume resembling it — into it beforehand. Loosen all of the straps completely and then tighten the sternum and side adjustments until it feels secure but not constrictive.

If you have to try on an empty pack, rather than one loaded with gear, put the empty vest on without tightening the sternum strap, leaving a gap of a few inches across your chest between the shoulder straps. This will allow for adjustments once the pack is fully loaded with fluids and gear.

Some packs offer a sliding rail to adjust the position of the sternum straps, while others have a hook or “T” attachment with several fabric loops along the front to allow you to customize the fit by changing the position of the straps across your chest. This extra layer of adjustability across the chest is great to allow runners of all shapes and sizes to use a pack. The hydration pack should fit snugly but not restrictively, and you should be able to twist your trunk, swing your arms, and breathe easily without the pack shifting or excessively bouncing.

Some packs come in a gender-specific fit, which can mean anything from smaller sizes and different colorways to a completely different pocket and hydration-carrying configuration. It’s important to note that these changes don’t always translate to a better fit. For example, many of our testers, regardless of gender, prefer the fit of the unisex Salomon Adv Skin 12 and Salomon Adv Skin 5 over the women’s-specific option. The takeaway here is to consider your body type and do a little research into the size ranges and existing reviews for the pack to help guide your decision.

When temperatures rise, a hydration vest will allow you to carry the water you need on a run. Unfortunately, adding a hydration pack also adds extra material on your back and chest that can increase heat retention and sweating. The breathability of a pack is crucial to mitigate this effect and keep you comfortable when running in the heat.

In general, the two factors that most impact the pack’s breathability are the inner mesh that contacts your body and the outer body material. All of the packs we tested have some type of lightweight mesh material lining next to the body, usually polyester, that is perforated or honeycombed to improve ventilation and moisture wicking. The place where heat retention of the pack really differs is in the rear pocket and outer pack materials.

Packs that scored very highly among testers for breathability such as the UltrAspire Spry 3.0 Race Vest, UltrAspire Alpha 5.0 Race Vest, Kailas Fuga Air II Trail Running Hydration Vest Pack 5L, and USWE Pace 8L Trail Running Vest all have a mesh lining and pockets that are made of lightweight stretchy materials to allow for good airflow. There are no water-resistant panels to retain moisture and heat, and any insulating panels are removable to improve breathability when you need it.

In contrast, some of our other top picks such as the CamelBak Ultra Pro Vest, Salomon Adv Skin 5, Salomon Adv Skin 12, and the UltrAspire Zygos 5.0 Hydration Pack have nylon panels or outer pocket materials that improve durability and moisture protection but increase heat retention. All of these are great packs that our testing team ranked very highly, but if you are routinely running in hot conditions or have a high sweat rate, the breathability factor will weigh more heavily than for those who run more frequently in cool, dry conditions.

The main point of a running hydration pack is, well, hydration! For short runs and moderate temperatures, a handheld or waistbelt can suffice, but when you are tackling hours on the trails in hot humid conditions, you’ll need more fluids to keep you going and a good way to carry them.

The water capacity of running hydration packs varies based on pack size. Smaller packs can typically hold around one liter of fluids, while larger packs meant for longer runs can hold three liters or more. Most hydration packs carry fluids in two ways: soft flasks that sit in front pockets on the chest and in a hydration reservoir, commonly referred to as a bladder, that fits in a rear compartment on your back.

All but the smallest packs have the option to use both, allowing you to easily expand the amount of water you can carry. There is no right or wrong in the debate between flasks or hydration bladder, it simply comes down to comfort and personal preference.

Testing trail running pole storage on the Salomon Adv Skin 12 Unisex Running Vest in Colorado. This pack earned high honors in the large-capacity category of this guide. Photo: iRunFar/Eszter Horanyi

The amount of water-carrying capacity you need in your pack should be determined by the type of terrain and conditions you most frequently encounter. For shorter runs or races with frequent aid stations, a smaller capacity pack will do the trick. Easy access to water sources such as stream crossings can also lighten your load, as you will be able to filter water along the way — check out our best water purification for trail running guide for some of our favorite water filters to carry out on the trails. For long days without easy access to water or in very hot weather, a larger pack that can fit at least a two-liter reservoir as well as two 500-milliliter flasks in front is the best choice.

As we mentioned above, running hydration packs have two ways to carry water: flasks or bottles and a hydration bladder. The right choice comes down to weighing comfort, ease of access, and the amount of water you will need to carry — and in some cases, you will be using both!

The earliest versions of hydration packs were essentially a water bag inside a backpack. While the technology has changed tremendously, a hydration bladder in the back of the pack is still a go-to for most hydration packs. Even if the pack does not come with a bladder, as many have switched to include front flasks only, there is usually a pocket to accommodate a hydration reservoir in all but the smallest of packs.

There are definitely some pros to using the reservoir, including increasing your liquid-carrying capacity, as most packs can fit up to two liters this way. This also frees up front pockets for stashing essentials like nutrition and your phone in an easy-to-reach place. On the negative side, hydration bladders tend to slosh more if there is any excess air in them and add extra weight to your back, which some runners might not prefer. It is more difficult to keep track of how much you are drinking with the bladder since it is out of sight and requires you to remove your pack to get to the reservoir to refill it.

While there are a few running vest options that have a rear bottle holster, the majority of running hydration packs use bottles or collapsible soft flasks in pockets on the front of the vest over the chest. The usual capacity of these is about 500 to 600 milliliters (20 ounces). Soft flasks give quick access to your fluids, making it easy to refill without having to take the pack off. They also make it much easier to mix and match your hydration needs with electrolyte drink mixes, plain water, or even soda (because sometimes ginger ale or Coke are the only things that work, amiright?)

On the downside, two 500-milliliter soft flasks will only give you one liter of liquid capacity. They also usually sit in front pockets over the chest, which may be uncomfortable for some runners, especially those with larger chests.

While hydration may be the primary function of your running pack, the gear storage is what sets the best packs ahead of the rest. The pocket size and placement are crucial to the organization and functionality of the pack. Easy access to essentials on the go and secure storage for extra gear and valuables are key features of all of our favorite packs.

The most common pocket arrangement for running hydration packs is a combination of smaller front pockets and larger rear compartments, with some packs utilizing the material under the arms for storage as well. The best pockets are stretchy enough to expand their capacity while being elastic enough to prevent sagging and bouncing and to keep your gear secure.

Front pockets are found on pretty much all running hydration packs on the market today, and for good reason! Front pockets are usually separated into a pocket designed to hold a soft flask and additional compartments overlying the soft flask pockets for storage. These make it super easy to stash and access frequently needed small items such as nutrition, lip balm, a cellphone, and more without having to worry about removing your pack.

Most pockets are made of stretchy material to expand for easy stowing and to keep items secure when moving. Most packs have at least one zipper pocket to keep a key, money, or other important items secure. Many packs also have smaller pouches on the shoulder straps to store very small things like salt tabs.

All but the smallest running hydration packs have at least one storage pocket on the back, usually a pouch spanning the length of the pack that holds the hydration bladder and can serve as a stuff sack for a jacket, extra layers, a first-aid kit, and other gear that does not need to be quickly accessible. Most running vests add additional storage capacity by adding stretchy overlay pockets onto the larger back compartment to provide extra room without adding excessive weight.

Common rear storage and pocket arrangements include an inner sleeve inside a single large rear pocket to separate it into two compartments, top-loading or kangaroo-type tunnel pocket across the bottom for access without removing the pack, open stuff pocket on the outer part of the pack, or bungee cinch cord attached to the outer compartment. All of our favorite packs feature some combination of these to maximize gear capacity without adding bulk.

The best pocket setup is entirely subjective and will vary from runner to runner and depend on what type of racing or terrain you run on the most. Minimalists will reach for a lightweight pack for simple essentials, while mountain runners spending hours in remote terrain will have much bigger gear storage needs. Runners with shoulder mobility issues may not be able to reach behind their back to access gear from a rear pocket with their pack on.

In addition to the basic storage setup of the pack, there are a few extra details that are worth considering depending on your intended use. Secure closures, such as zippers, Velcro, or clasps, are an important consideration if you will be doing a lot of bending or scrambling or taking your pack on and off frequently to avoid inadvertently dropping or losing important gear.

A water-resistant pocket for valuables such as your key or cellphone may be an important addition in wet climates or all-day rainy ultras. Perhaps the most important pocket add-on detail is a key clip — because no one wants to get back to their car or home to find that their key dropped out of their pocket somewhere along the trail.

A hydration pack allows you to extend the range of your trail runs since you can carry liquids, snacks, and gear. Photo: iRunFar/Eszter Horanyi

The chest strap closure system is a small detail with a big impact on the fit and functionality of a hydration vest. There are a number of different methods utilized for the chest strap closures, but overall our testing team agreed that no matter the type, simplicity, and ease of use are hands down the most important features of any clasp.

The most common chest strap closure is a simple buckle, and for good reason. Similar to a traditional backpack sternum closure, these are easy to use and typically do not require a great deal of focus or dexterity, important for cold fingers and tired brains. The straps are quickly and easily adjustable by simply pulling them tighter or looser at the buckle.

Many of our tested pack manufacturers, including Nathan, Ultimate Direction, and CamelBak, utilize buckle closures on their sternum straps, and our testers appreciated their ease of use. In the case of the USWE Pace 8L Trail Running Vest, one large single buckle centered on the chest is about as simple as it gets! The Osprey Duro 1.5 and Kailas Fuga Air II Trail Running Hydration Vest Pack 5L employ a slightly different variation of the plastic buckle closure, with plastic clips attached to the sternum straps that clip on to an attachment along the front of the pack.

Another commonly used chest strap closure is a cord that stretches across the chest and attaches to a plastic hook. The strap is then adjusted by pulling the cord through a bungee clasp system to easily tighten and loosen as needed. The Salomon Adv Skin 5, Salomon Adv Skin 12, UltrAspire Alpha 5.0 Race Vest, UltrAspire Zygos 5.0 Hydration Pack, and the UltrAspire Spry 3.0 Race Vest — all of which are included in this guide — use some form of this closure.

The adjustability on the fly and stretch with chest expansion while breathing are features our testers found very positive. These closures do require a bit more dexterity to align the strap over the hooks, and thus can be tricky in very cold conditions with gloves on or for runners who have trouble with fine motor movements with their fingers.

Hydration packs are an expensive piece of gear and a significant investment for most runners that we hope to last and withstand years of water carrying, gear toting, and trail running. The durability of a pack depends on the type of fabrics, clasps, and cords used in its construction, as well as your use and care of the pack.

A failure of a zipper, pocket, or clasp could range from minor inconvenience to catastrophe if you have a gear failure in remote terrain, so your intended use of the pack and the terrain you plan to run on should be factored into choosing the best pack for you. Someone whose runs take them to remote mountain ridges or bushwhacking through trees and rocky terrain will have different durability requirements for a pack than someone who mostly runs on gravel roads.

As with many other pieces of trail running and outdoor gear, when material weights decrease, durability follows. Running hydration packs tread a fine line when it comes to the thickness and weight of the materials and maintaining durability, both of the fabrics as well as straps, cinch cords, buckles, and clasps. All of the packs we tested fared well in terms of their durability with no major tears or breakage in our testing period.

Some packs, such as the Salomon Adv Skin 5 and Salomon Adv Skin 12, have been in use by our testers for much longer and there were no reported issues with their durability. In general, all of the running hydration packs tested for this guide are made of a combination of stretchy mesh materials and nylon panels to optimize the balance between gear capacity, weight, and durability.

Some packs, like the CamelBak Ultra Pro Vest, UltrAspire Zygos 5.0, and Ultimate Direction Mountain Vest 5.0 have more nylon ripstop materials to prevent snagging and potential tears, while others like the Kailas Fuga Air II Trail Running Hydration Vest Pack 5L and USWE Pace 8L Trail Running Vest are lighter weight mesh and stretch materials.

As detailed above, the closure systems between packs vary as well, and fatigue of the clasps and buckles should be considered in terms of the pack’s overall durability. A runner that will be frequently removing the pack may want a system like the stretch cords of the Salomon or UltrAspire packs versus a plastic buckle or clip found on the Osprey or Kailas packs to decrease the potential for a broken clip.

As we discussed in the above sections, there are a lot of thoughtful details that have gone into the design and construction of running vests that have made them a crucial piece of gear for most trail and ultra runners today. In addition to the pocket layout, materials, and fit, there are several additional features that enhance safety and the functionality of the pack.

Kyle Curtin using an Ultimate Direction hydration pack on a run in Colorado. Photo: iRunFar/Eszter Horanyi

As with all of these guides, our testing process began with extensive research into the running hydration packs and running vests available on the market today. After compiling a list of over 130 packs, we narrowed it to 25 for intensive testing.

We spent several months piling water and gear into our packs and hitting the trails from humid U.S. East Coast ultramarathons to high-elevation mountain terrain and everything in between. We put these packs through the wringer to come up with a list of our favorite picks for your next trail adventure.

When should I run with a hydration pack?

The temperature, terrain, and duration of your run, in addition to personal preference, will all play a role in answering this question. A good rule of thumb is to consider running with a pack if you will be out for more than an hour or two, as this will ensure that you have enough fluids and nutrition to get you through your run or race. In hotter temperatures, you may want to load up on extra water or carry a pack for even shorter runs to avoid dehydration and overheating.

Runs in more remote locations or difficult terrain may require extra gear, like a first-aid kit or trekking poles, and keeping your hands free by wearing a pack will make life much easier even if you aren’t heading out for a long run. Any multi-hour adventure and almost all ultramarathon races will require a pack to allow you to carry the gear, food, and water needed for a safe and comfortable day on the trails.

I frequently reach for a smaller pack on almost all of my runs, as it gives me an easy place to store my phone, a little water, and some dog treats while keeping my hands free to wrangle my four-legged running buddy’s leash.

What capacity hydration pack do I need?

This is largely dependent on the type of running or racing you intend to do. The smaller capacity packs in the one- to five-liter range are perfect for shorter runs and races where minimal gear and hydration are needed, such as a two-hour run, well-supported ultramarathon with frequent aid, or a two- to four-mile repeating loop course where you may not want a bottle in your hand the entire time but don’t need to carry hours worth of nutrition or gear.

A mid-capacity pack in the six- to 11-liter range will give you extra storage space for food, fluids, and layers to extend your unsupported running time. For all-day runs or high mountain adventures where multiple extra layers and safety equipment will be required regardless of the run length, a high-capacity 12-plus-liter pack will be the way to go.

Don’t want to have a closet full of packs? Don’t worry! Most of the higher-capacity packs are made of lightweight stretchy materials that are made to fit close to your body when not full, so if you need one pack to take you through both your two-hour training runs and your ultramarathon on race day, these will expand to fit gear and also wear comfortably when not stuffed to the gills.

How should my running hydration pack fit?

Your pack should fit snugly against your body to avoid shifting and bouncing with movement. This improves comfort and hopefully eliminates friction and chafing from the materials. You will want enough room in the arms to have unrestricted arm swing and enough room in the chest to be able to tighten the sternum straps to secure the pack but not restrict breathing.

The best running vests are made to sit high on the back and torso to keep things stable while moving quickly. All pack manufacturers included in this buyer’s guide have a size chart for their packs along with instructions on how to take proper measurements to ensure an accurate fit. That being said, some packs just fit bigger or smaller than expected even when measurements are taken, so there is definitely some trial and error involved in finding your perfect fit.

We tested the storage pockets on a number of hydration packs to see what allows accessibility and organization for trail running the best. Here, Jeff Rome tries out the pockets on a Patagonia hydration pack. Photo: iRunFar/Eszter Horanyi

What should I carry in my running hydration pack?

First and foremost, running hydration packs are made to carry water, so any pack you choose should have a comfortable way for you to carry your hydration. Once you square away your fluid carrying in soft flasks, bottles, or a bladder, you will need to look at the type of event or run you are doing and plan accordingly. Food, energy gels, and electrolyte powder are important for unsupported events or sensitive stomachs.

Depending on the weather, a hat, gloves, buff, jacket, or extra layer may be in order. An emergency blanket and small first-aid kit are never a bad idea to have on hand. At the very least, some band-aids and tape will help in a pinch. A cellphone for safety, music, and photos is a must-have for most of us! For long days, a small external charger for a phone may also make the cut. The moral of the story is that hydration, food, and safety should always be at the top of your packing list.

Is there a difference between a men’s and women’s hydration pack?

The answer here is … sometimes. As we noted above, the Salomon Adv Skin 5, Salomon Adv Skin 12, and CamelBak Ultra Pro Vest all have a men’s or unisex version and a women’s-specific version that have different layouts and pocket configurations that change the fit of the vest. Other brands have men’s and women’s versions that differ in colorways and sizing range, but the general layout and capacity of the pack are unchanged. Many others have one unisex version.

The gender-specific designation typically doesn’t mean much in terms of the actual technical specifications and function of the pack — it simply changes the fit. We always recommend runners choose the layout, setup, sizing, or color that suits them the best regardless of whether it is labeled men’s or women’s.

Should I carry my liquids in bottles and soft flasks or in a hydration bladder?

This is very much a matter of personal preference and may take some experimenting to see which setup you prefer. For faster runs or races where quick aid station turnaround is important, a flask or bottle is much easier to remove, refill, and replace than a bladder. For very hot days or long runs, a bladder may be preferable for its additional volume, or a combination of both can be used to ensure you have adequate fluids.

How can I reduce liquid sloshing in the hydration bladder?

Hydration bladder sloshing is caused by extra air in the reservoir, creating space for water to splash around. To fix the annoying slosh, you need to remove the air. The best way to do this is to turn the hydration bladder upside down after filling it and suck through the tubing until the air is removed and you have drunk some of the water. Once you turn it right side up, the air is gone and so is the slosh!

How do I prevent chafing from my hydration pack?

Chafing is caused by friction. If you can eliminate excess friction, you will eliminate, or at least improve, the chafing problem. A properly fitting pack is the first step — packs that are too big will move around and rub, and a pack that is too tight will cause pressure points.

Once pack fit is dialed in, a generous application of your favorite running lube on areas like the shoulders, back of the neck, bra strap, and underarms can help reduce chafing with normal running movements. Keeping a barrier between your skin and the pack can also help, so runners that prefer to go shirtless may need to wear at least a light layer if chafing becomes a problem.

What are the best hydration packs for larger chests?

There are a number of packs that have features designed to improve comfort over the chest area. Women-specific models of packs often place the front soft flask pockets lower on the strap than on the unisex model to avoid compressing the chest. Many runners find front flasks to be uncomfortable over the chest and may find a better fit by using a rear hydration bladder only.

The sternum strap configuration and shoulder strap shape are other factors that can affect comfort over larger chests. Sternum straps that have adjustable positions and some stretch to the straps themselves will likely be more comfortable than a rigid or fixed-position strap, which may lead to increased pressure. The curved front straps and positioning of elastic sternum straps on the UltrAspire Astral 4.0 Race Vest, which UltrAspire dubs their HerFit Harness, are made to fit comfortably around the chest, avoiding direct pressure over the breasts.

While there are multiple pack offerings with design elements made to better fit women’s bodies, the most important factor to consider is what is most comfortable for you. A larger-sized unisex pack may end up being a better fit than one marketed as women’s specific for many people, so some trial and error, and a good return policy, may be in order.

Glass Filled Nylon Block We should note that in the testing round for this guide, we did not have any larger-chested runners to provide detailed feedback about this. Specific pack recommendations for large-chested runners will be added to this guide as we complete future testing.