Katadyn BeFree vs LifeStraw Peak vs HydraPak UltraFlask vs Salomon XA
Comparing all half liter sized soft flasks with 42mm filters
This buyer’s guide to the best soft flask filters compares three top models for trail running and hiking within an actively proliferating sub-genre of backcountry water purification. What was once a category invented and occupied only by Katadyn BeFree, is now competitive due to the advent of LifeStraw Peak Squeeze, HydraPak UltraFlask + Filter Cap, and the Salomon XA. While all models are similar, each has distinct features, pros, and cons relative to the others. Here is shortcut for how to choose:
- HydraPak UltraFlask + Filter Cap is best for front-pocket-mounting, and trail runners. Bite valve is fastest to drink from. More prone to spillage and awkward for filtering into other vessels. Shop now.
- Katadyn BeFree AC is the most versatile option for hikers, with a new and improved flip cap. Optional activated carbon filter improves taste but decreases flow rate. Shop now.
- LifeStraw Peak Squeeze is the least expensive, longest lasting, and most durable unit, but also the heaviest, bulkiest, and worst for front-mounting. Shop now.
- Salomon Soft Flask XA is the original bite valve filter with the lightest weight and skinniest flask. But it’s slightly too tall for most pockets, and we generally prefer the longer-lasting, back-flush compatible HydraPak Ultraflask. Shop now.
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Why 500ml sized models? The reason we recommend soft flask filters in the half liter capacity range is because they’re small enough to be front mounted in running vests and shoulder strap pockets. Front mounting is the most efficient backcountry hydration system because it allows users to refill and drink water faster for the least amount of effort. We recommend against 1L sized soft flasks because they require side pocket storage, which is an area better suited for hard-sided bottles.
While you’re here, check out more hydration gear guides, including water storage, ultralight bottles, ultralight bladders, all squeeze filters, and shoulder strap bottle pockets.
Pros and Cons of Half Liter Sized Soft Flask Filters
Pros of All Soft Flask Filters
- Most efficient filtration system possible when front-mounted in running vests or shoulder strap pockets
- Ease of filtration allows you to store less excess water in bottles and reservoirs when water is abundant
- Hollow fiber filter removes most common contaminants
- Lightweight and collapsible body with reinforced top
- Easy to drink from, very fast flow rate when new
- 42mm threaded opening
- Can be used to filter into other vessels
Cons of All Soft Flask Filters
- TPU body material imparts plastic-y flavor at first
- Less durable, less reliable, less long lasting than Sawyer Squeeze-style filters
- Flow rate decreases with usage, cleaning helps but only buys time
- Freezing damages the filter
- Lower volume means more dips into water source
Soft Flask Filter Comparison Table
Mobile users rotate device for full-width table view
| Make & Model | Price ($) | Volume (ml) | List Weight Dry (oz) | Claimed flow rate (liters per minute) | Claimed Filtration Lifespan (L) | Widest Width (in) | Length (in) | Cap Style | Measured thickness, 8 folds of sidewall (mm) |
Cleaning Options
|
| Katadyn BeFree AC | 45 | 500 | 2.5 | 2 | 1000 | 3.3 | 10.75 | Flip | 2.3 | Swish |
| HydraPak UltraFlask | 50 | 500 | 2.3 | >1 | 1500 | 2.5 | 9.50 | Bite | 3.4 | Swish or Flush |
| LifeStraw Peak | 38 | 650 | 3.6 | 3 | 2000 | 4.8 | 10.00 | Screw | 4.4 | Flush |
| Salomon XA | 50 | 500 | 1.8 | N/A | 1000 | 2.4 | 11.80 | Bite | 2.0 | Swish |
| Cnoc Hydriam + 42mm Cap | 48 | 500 | 3.1 | >1 | 1500 | 3.0 | 8.50 | Screw & Flip | 2.5 | Swish |
Katadyn BeFree AC
Katadyn BeFree is the original soft flask filter that invented this sub-genre back in 2016, and is by a large margin the best-selling and most well-known model of its kind. The updated-for-2025 Katadyn BeFree AC is still the best option for most hikers, and builds on its predecessor’s success using the same filter technology, but with a redesigned body, sturdier cap, and the addition of an optional activated carbon filter to improve taste. It remains the option that most people should choose because it is the most versatile and well-rounded option in the category. See more in our Katadyn BeFree AC Review.
- Price: $45
- Volume: 500ml
- Weight: 2.5 oz
- Relative Pros: Best for hikers. Lightweight. Fast flow. Burly head. Activated Carbon eliminates bad tastes, including TPU. Invented the genre. Best seller by far.
- Relative Cons: Thinner TPU sidewall material. Optional secondary activated carbon filter significantly reduces flow rate. No backflush. Tall. Clip attachment point is unnecessarily large. Shortest lifespan.
BeFree’s primary hollow fiber filter unit is unchanged from its predecessor, which means easy swish cleaning in the field, and very fast flow rate when new. But that also means a diminished flow rate over time and no back flush capabilities.
The new activated carbon filter works to improve the taste of the water, including removal of new TPU plastic taste. When new, inclusion of the activated carbon filter decreases flow rate by a bit less than half. However, once the flow rate of the primary hollow fiber filter takes on particles with use and decreases to an approximate mid-life steady state, the amount in which the activated carbon filter decreases flow rate becomes less perceptible.
Its reinforced flip top cap with metal hinge feels very durable, and is a big improvement over its breakage-prone predecessor. It also includes a burly clip attachment point that is nice to have, but excessively large. The 500ml TPU body of the BeFree is 100ml smaller than its predecessor, which we view as an improvement for front-mounting, and it’s folded over at the base instead of connected to a secondary flat panel.
For those concerned about durability, a “BeFree Double Layer Edition” is also available, and built with a double thickness TPU. However, as it is only available in the 1L size capacity and is too large for front-mounting, we recommend choosing the LifeStraw Peak Squeeze 600 instead. But if you insist on a 1L BeFree, the double thickness version is better than the original.
Conclusion
On the whole, Katadyn BeFree AC is the most well-rounded and versatile soft flask filter for hiking and backpacking because it front mounts better than LifeStraw Peak Squeeze, and is less spillage-prone and better for filtering into other vessels than HydraPak UltraFlask + Filter Cap.
HydraPak UltraFlask + Filter Cap
HydraPak’s signature soft bottle, the UltraFlask, is already a mainstay in the running world due to its premier bite valve and vest-pocket-accommodating cylindrical shape. The new-for-2025 HydraPak UltraFlask + Filter Cap is the best soft flask filter for runners and front mounting. It is identical in filtration tech to Katadyn’s hollow fiber BeFree, and is the most efficient squeeze unit on the market for drinking out of directly. See more in our dedicated HydraPak UltraFlask + Filter Cap Review.
- Price: $50
- Volume: 500ml
- Weight: 2.3 oz
- Relative Pros: Best for runners. Smaller and lighter than most others. Well-shaped for front mounting. Bite valve is fastest to drink from. Swish and backflush cleanable. Minimalist backflush component mates with Smartwater.
- Relative Cons: Bite valve is more spillage prone than other caps. Must be front-mounted. Awkward for filtering into other vessels. Rated for slowest flow. TPU plastic taste at first.
HydraPak is first to market with a bite valve squeeze filter combo, and our first impression is that it works super well. Drinking out of it directly can be done one handed, and without even removing the filter from a front-mounted pocket. It is faster than the Katadyn BeFree AC flip top cap, and much faster than unscrewing the LifeStraw Peak Squeeze lid.
Another thing we like about the HydraPak UltraFlask body is that it’s cylindrical in shape, as opposed to the asymmetry of BeFree and Peak Squeeze. Those models widen at the head and flatten out at the ends. The reason UltraFlask fits into vests and shoulder strap pockets best is because it has the narrowest head, easing pressure on tight stretch mesh pocket openings.
The bite valve is pretty leakproof, but no bite-valve is perfect. We recommend against storing it anywhere but a front pocket, especially not inside your pack or at your feet in the tent when it’s full of water. Filtering from this into other vessels is possible if you squeeze the bite valve or temporarily remove it, but neither option is great and both present a wetter experience than other soft flask filters.
UltraFlask + Filter Cap is also the easiest unit to clean, and unlike the others, this can be done in multiple ways. For a quick and easy improvement to flow rate, simply conduct the swish and shake motion, as per Katadyn BeFree. For periodic deep cleans, it can also be back flushed, and comes with a very clever ultralight tool, perfect for the job. This component screws onto a 28mm threaded head (a la Smartwater Bottles), flushes at high pressure, and weighs virtually nothing.
Conclusion
Thanks to its bite valve and cylindrical shape, no competing alternative is as fast and efficient to use as HydraPak UltraFlask + Filter Cap, and none of them front mount as well. However, the fact that it’s more spillage prone and shouldn’t be stored inside a pack or on the tent floor while full makes it more awkward and less versatile for hikers and backpackers.
Lifestraw Peak Squeeze
Compared to its peers, LifeStraw Peak Squeeze filter is notable for enhanced durability, longer-than-average lifespan, and a lower than average price point. However, it’s also a bit heavier, bulkier, and slower to use than the others.
- Price: $38
- Volume: 650ml
- Weight: 3.6 oz
- Relative Pros: Fast flow. Least expensive. Thickest most durable sidewalls. Comes with back flush syringe. Clip attachment point.
- Relative Cons: Heavy. Screw-top cap slows drinking. Largest body doesn’t front mount as well. Cannot be swish cleaned. Backflush syringe adds weight. No volume measurement lines. TPU plastic taste at first.
For starters, LifeStraw Peak Squeeze’s hollow fiber filter is rated for the fastest flow and longest filtration lifespan in its class. Perhaps this is because it’s more Sawyer Squeeze-like than others. That is to say, while the Katadyn and HydraPak both have open-structure filter cages, the LifeStraw unit is more like a submerged Sawyer that only allows water in from the bottom, not the sides.
As such, it cannot be swish-cleaned, but it does come with a really nice backflush syringe. This device screws directly onto the filter for maximum flushing efficiency. While it is smaller than the infamous Sawyer syringe, it still weighs .8 oz, and is fairly annoying to carry into the backcountry; taking up precious space in your ditty bag.
Other notable features include the screw top cap. While it is arguably the most leakproof, it is also the most fiddly and slowest and least convenient for frequently drinking out of. A small plastic carabiner loop allows you to clip the Peak Squeeze for a more secure attachment.
The TPU plastic is extra thick, both measurably and touch-perceptibly burlier than what’s used by Katadyn or HydraPak. This adds puncture resistance, which works in conjunction with the longest filtration lifespan and burly lid to convince us it’s the most durable unit.
Conclusion
Despite the durability boost, it is the least efficient soft flask filter to use in the field, and hardest to front mount, leaving it as the third place option from our point of view.
Salomon Soft Flask Filter XA
French running juggernaut Salomon was first to market with a bite valve squeeze filter, releasing the XA 490 ml in 2021, and it remains the lightest weight option in the genre. And if you’ve heard of the concept of “forbidden snacks,” it definitely looks like one, a delicious blue raspberry popsicle.
- Price: $50
- Volume: 490 ml
- Weight: 1.8 oz
- Relative Pros: Lightest weight. Fast flow, fast bite valve drinking. Narrowest unit. Removable bail handle makes filling easy.
- Relative Cons: Tallest flask is too long for some pockets. Bite valve is more spillage prone than other caps. Must be front-mounted. Awkward for filtering into other vessels. Rated for shortest lifespan.
If the shape of your running vest pockets accommodate long skinny soft bottles best, look no further than the Salomon XA 490. Unlike its bite valve competitor the HydraPak UltraFlask, XA flattens out at the bottom, and is an inch taller in total length. This can be helpful if you want to leave it in the pocket while drinking, but is floppier and worse to drink from by itself. It may not fit shorter/shallower pockets when the flask is 100% full. Another advantage of this unit is that it is the lightest weight of all soft flask filters, though by a very small margin.
While it is otherwise nearly identical to the HydraPak Ultraflask – and in fact many of the components are made by HydraFlask – there are some key differences. UltraFlask uses a thicker TPU plastic, which is more abrasion resistant than the thinner Salomon (perhaps this accounts for the small weight difference. UltraFlask’s filter is rated to a lifespan of 1500 liters, compared to the 1000 of Salomon XA. What’s more, UltraFlask comes with a backflush tap, which helps maintain long term flow rate, while XA only gets shake and swish style cleaning.
Conclusion
The Salomon XA is a great filter for runners to front mount in tall skinny vest pockets, and it’s the lightest and easiest flask to fill up. However, XA is inferior to the HydrPak UltraFlask filter in terms of durability, shape, filtration lifespan, and backflush capability.
Cnoc Hydriam + HydraPak 42mm Filter
Representing the “build your own soft flask squeeze filter” category, here we’ll discuss two yet unfeatured components, the combination of Cnoc Hydriam 500 ml soft flask with HydraPak 42mm filter cap.
- Price: $48
- Volume: 500 ml
- Weight: 3.6 oz
- Relative Pros: Customizable. Combo of flip and twist opening makes it least spill-prone. Fast flow rate.
- Relative Cons: Upfront TPU taste. Most effort involved to open. Doesn’t back flush. Requires purchasing two separate components. shortest/widest unit in 500 ml class.
First off, Hydriam 500 ml is a standalone soft flask that is also compatible with BeFree and HydraPak Bite Valve filters. It is also available in 350 ml and 750 ml sizes. A 28 mm threaded version is also available, and it fits filters from the Sawyer Squeeze or Platypus QuickDraw family.
The Hydriam soft flask itself is the shortest and widest unit out there, which may be desirable depending on the pocket configuration. It is made by Cnoc, who also manufactures the most popular bladder on the PCT – VectoX. One minor complaint we have with Cnoc products is that they always seem to have more up front TPU taste than other brands.
It may not be as fast or efficient as the bite valve filters, but don’t sleep on HydraPak’s original 42 mm filter cap. It is the same hollow fiber filter as the aforementioned bite valve version, but closes off much more securely due to the combination of both twist and flip closure mechanisms. As such, it has the most secure seal of all soft flask filters we tested, and is great for filtering into other vessels.
Conclusion
This specific combination of soft flask and filter head yields the shortest height and most secure closure. We encourage testing other combinations to see which pairing suits you best!
How to Choose Between our 3 favorites: Katadyn BeFree AC vs HydraPak UltraFlask vs Lifestraw Peak Squeeze
This section is an expanded version of the overview we gave at the top of the article.
Choose Katadyn BeFree because it offers the best overall blend of performance characteristics for hiking and backpacking.
It is conveniently shaped and narrow enough for front mounting into shoulder strap pockets; much better than LifeStraw Peak Squeeze, albeit not quite as ideal as HydraPak UltraFlask. Its flip top cap is the right blend of fast and spill proof – faster than LifeStraw but a smidge less spill-proof, slower than HydraPak, but much more spill-proof. It is easier to use for filtering into other vessels than UtraFlask, but ties LifeStraw in that regard.
The activated carbon is a cool add-on and having the option to use it is strictly upside, but usage thereof comes with pros and cons. We like that it removes the TPU flavor and other backcountry taste degraders liken sulfur, and tannins, but that comes at a fairly large cost of decreasing its flow rate
Choose HydraPak UltraFlask + Filter Cap is best for trail runners because it is the most effective unit for front mounting, and the fastest to drink out of directly. It is fastest to drink out of because of the bite valve, which removes a step in the process, meaning you don’t have to flip open or unscrew a cap. The bite valve also allows you to drink directly from the front mounted position by simply bending your head forward and down.
The narrow, perfectly cylindrical body shape makes it easier to slide in and out of tightly fitted mesh pockets. This differentiates it from the slightly wider and taller Katadyn BeFree, and the much wider and thicker LifeStraw Peak Squeeze.
As a notable downside, this HydraPak UltraFlask is the worst option for filtering into other vessels, as the bite valve must either be squeezed or temporarily removed.
Choose LifeStraw Peak Squeeze because you value longevity, durability, reliability, and cost-savings over on-trail efficiency. This unit costs $10 less than it peers, is built with thicker TPU, and its filter is rated to last 1.5-2x longer. It also has the most effective flushing mechanism and fastest flow rate. As a reminder, this is the largest, bulkiest unit, and not recommended for use with running vests.
Soft Flask Filter Conclusion
Thank you for reading our guide to soft flask squeeze filters, where will continue to monitor this sub-genre and keep you up to date on the best options. To wrap up, we reiterate that front mounting a soft flask squeeze filter is the fastest and most efficient way to hydrate on the trail, and we hope you’ll give it a try. Happy trails!
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