Cnoc Outdoors
Cnoc Hydriam 500 ml Collapsible Flask (28 mm)
- Weight for its size: 10/10 How much it adds to your pack for the water it holds.
- Packed size (empty): 9/10 How much room it takes up when it is empty, for the water it holds.
Running-vest pockets: tapered shape, 25 x 9 cm when full (Cnoc)
- Type
- Soft
- Capacity
- 0.5 L
- Weight
- 26 g
Packed size 0.094 L, 7.5 cm long and 4 cm across Compare with a 2-litre bottle
Shorter than a 2-litre bottle and thinner than one. Drawn to scale.
Where to buy
Ultralight Outdoor Gear £18.99 In stock. Free delivery. Free tracked UK delivery on all orders (header: free over £15).
View at shop: Ultralight Outdoor GearPrices 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 10/10How much it adds to your pack for the water it holds. 10: The best you can buy for this.
Cnoc's page says 25.5 g for 500 ml (we round up to 26 g in the spec): 51 g per litre, under 100 g/L. Ultralight Outdoor Gear lists 24 g, which bands the same.
Packed size (empty)
From maker's figures 9/10How much room it takes up when it is empty, for the water it holds. 9: Among the best you can buy for this.
Cnoc gives a packed size of 7.5 x 4 x 4 cm: two equal smaller sides, so a roll 7.5 cm long and 4 cm across. 3.1416 x 2 x 2 x 7.5 = 94 cm³, so 0.094 L empty for 0.5 L held: 0.19 L per litre, under 0.3.
In short
Good for
- Running-vest pockets: tapered shape, 25 x 9 cm when full (Cnoc)
- A small second bottle or flask that rolls to 7.5 cm
- Filtering on the move with a 28 mm filter such as the Sawyer or Platypus QuickDraw (Cnoc)
Strengths
- 25.5 g for 500 ml (51 g per litre), under the 100 g/L line for the top weight score
- Rolls up to 7.5 x 4 x 4 cm, 0.19 L per litre held
- Tethered cap and 28 mm thread (Cnoc)
- Measuring marks on the back (Cnoc)
Weaknesses
- Rated only from -6 °C to 49 °C, so not for hot drinks (Cnoc)
- TPU is porous: Cnoc says it is not completely smell-free when new, so wash and air it first
- Small, 500 ml: a flask, not a main bottle
- Ultralight Outdoor Gear lists 24 g against Cnoc's 25.5 g, which we use
- No independent test found, so ease of use and durability are estimates, not reviewed scores
- Only one UK shop found
Sources
We haven't tested this ourselves. Every score comes from these specs, tests and reviews.