Cocoon
Cocoon Drybag Hyperlight (21 L)
- Waterproof build: 6/10 How well its build keeps water out, from the published seams, closure and submersion claim.
- Weight for its size: 10/10 How much it adds to your pack for the space it protects.
A very light, semi-transparent pack liner or organiser for clothes and sleep gear inside a rucksack
- Capacity
- 21 L
- Weight
- 48 g
- Seams
- Taped
- Closure
- Roll top
- Fabric
- 15 denier
Where to buy
Vampire Outdoors £25.95 In stock. Delivery £3.99. 21 L Dried Reed variant. Delivers within the UK only; £3.99 under £100, free over £100.
View at shop: Vampire OutdoorsUltralight Outdoor Gear £25.99 In stock. Free delivery. 21 L price, the same in Dried Reed and Coral Grey. Free UK delivery on orders over £15 (Royal Mail Tracked 48).
View at shop: Ultralight Outdoor GearPrices checked 2 Nov 2026 to 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
Waterproof build
From maker's figures 6/10How well its build keeps water out, from the published seams, closure and submersion claim. 6: A bit better than average.
Cocoon says the seams are taped on the inside (PU-coated, siliconised 15D nylon) and the bag needs three rolls and the buckle to be waterproof. It says "Do not submerge in water", so there is no submersion claim: the 3 band.
Weight for its size
From maker's figures 10/10How much it adds to your pack for the space it protects. 10: The best you can buy for this.
48 g for 21 L is 2.3 g/L, under 4.0 g/L (Cocoon's size chart; Ultralight Outdoor Gear lists the same 48 g).
In short
Good for
- A very light, semi-transparent pack liner or organiser for clothes and sleep gear inside a rucksack
- Cutting pack weight where the bag stays inside the pack
- Not for river crossings or anything that may go under water
Strengths
- 48 g for 21 L (2.3 g/L)
- Recycled 15D nylon, semi-transparent so contents show
- Taped seams on the inside, with a roll-top and buckle
- D-ring and bottom loop to hang it dry or strap it on
- Seven sizes from 1.5 to 37 L
Weaknesses
- Cocoon says do not submerge it
- 15D fabric is thin: keep it inside the pack
- No independent tests found, so durability and ease are estimates, not reviewed scores
Sources
We haven't tested this ourselves. Every score comes from these specs, tests and reviews.