HydraPak
HydraPak Stow 500 ml Flexible Bottle
- Weight for its size: 9/10 How much it adds to your pack for the water it holds.
- Packed size (empty): 8/10 How much room it takes up when it is empty, for the water it holds.
Lowest price we found
£17.99 at Ultralight Outdoor Gear
Go to Ultralight Outdoor Gear Compare 3 shopsShort walks and day trips where a small bottle should vanish into a pocket
- Type
- Soft
- Capacity
- 0.5 L
- Weight
- 40 g
- Packed
- Not published
Where to buy
Ultralight Outdoor Gear £17.99 In stock. Free delivery. It lists 40 g and 500 ml.
View at shop: Ultralight Outdoor GearSportsshoes £17.99 In stock. Delivery £4.99. Standard+ 48 UK delivery £4.99 on its page. Its site-wide discount code is not included in the price.
View at shop: SportsshoesHydraPak £18 In stock. Delivery £3.60. Three colours in stock. HydraPak's UK shop. Free UK delivery over £50 on its shipping page (£75 on its shipping policy page); under that it is £3.60 by Royal Mail Tracked 48 or £6.00 by DPD next day.
View at shop: HydraPakPrices checked 8 Nov 2026 on each shop's own page; shops can change them. We earn no commission on these links; shops are listed by price. More
Our ratings (out of 10)
1 to 10, compared with the whole market. Each says what it's based on. How we score
Weight for its size
From maker's figures 9/10How much it adds to your pack for the water it holds. 9: Among the best you can buy for this.
HydraPak lists 40 g for 0.5 L (UK and US pages agree): 80 g per litre, under 100 g/L. Ultralight Outdoor Gear and Sportsshoes list the same 40 g.
Packed size (empty)
Estimate from maker's specs: soft bottle: rolls up when empty 8/10How much room it takes up when it is empty, for the water it holds. 8: Clearly better than most.
Estimate from maker's specs
What reviewers say (out of 10)
Ratings marked * are from reviews and are not part of the trip score. They are reviewers' scores, not our own measurements. How we score
Leakproof*
Reviewers' average 9/10How reliably it stays sealed in a packed rucksack.
3 reviews on leakproof, e.g. "They have been leak proof and functioning properly since I've had them.".
Durability*
Estimate: only 2 reviews about durability (fewer than the 3 we need, so never above 8) 8/10How well it survives knocks, drops and daily use.
2 reviews on durability, e.g. "They have been leak proof and functioning properly since I've had them.".
In short
Good for
- Short walks and day trips where a small bottle should vanish into a pocket
- The dirty-water bottle for a squeeze filter with a 28 mm thread
Strengths
- 40 g for 0.5 L, about 80 g per litre
- Rolls up when empty and stows in its bail handle
- Flip-top cap protects the spill-proof silicone nozzle
- Fits most 28 mm threaded filters, including HydraPak's own 28 mm filter kit
- One reviewer has used both sizes leak-free for over two years
- Beyond Lifetime Guarantee on defects
Weaknesses
- A floppy, slightly awkward feel, more so on the 1 L (Find Your Haven)
- You have to squeeze or suck to drink, which took one reviewer time to get used to (Raw Family DIY TV)
- Holds only 500 ml, so a day on the hill needs a second bottle
- Only 1 source on this size reports wear, so durability is an estimate, not a reviewed score
- HydraPak gives no rolled size, so the packed size is an estimate, not a reviewed score
Sources
We haven't tested this ourselves. Every score comes from these specs, tests and reviews.
ShowHide sources (6)
- HydraPak: Stow 500 ml collapsible water bottle (spec page)
- Toolsdoctor (YouTube): Tested, HydraPak Stow full review (1 L and 500 mL, with the flip cap)
- Raw Family DIY TV (YouTube): HydraPak Stow collapsible backpacking water bottle (both sizes, bought the 500 mL by mistake)
- Find Your Haven Outdoors: Review, HydraPak Stow collapsible water bottle (over two years of use, 1 L and 500 mL)
- HydraPak customer reviews: Stow 500ml (144 of the 248 on the shared Stow feed, incl. Mountain, Protect Our Winters and LTE Winter prints; 110 flagged verified buyers; all 248 read; maker's own Okendo feed)
- HydraPak customer reviews: Stow 500ml (144 of the 248 on the shared Stow feed, incl. Mountain, Protect Our Winters and LTE Winter prints; 110 flagged verified buyers; all 248 read; maker's own Okendo feed)