Osprey
Osprey Ultralight Pack Liner Small (36 L)
- Waterproof build: 5/10 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.
Lowest price we found
£28.99 at Ultralight Outdoor Gear
Go to Ultralight Outdoor Gear Compare 3 shopsWaterproofing the inside of a 30 to 50 L rucksack with one light bag instead of several dry bags
- Capacity
- 36 L
- Weight
- 91 g
- Seams
- Not published
- Closure
- Roll top
- Fabric
- 40 denier
Where to buy
Ultralight Outdoor Gear £28.99 In stock. Free delivery. Small, black, in stock (checked on the size). RRP £29.99. Free tracked UK delivery on all orders.
View at shop: Ultralight Outdoor GearGO Outdoors £30 In stock. Delivery £3.99. Member's price £24 (not included). Free delivery over £80.
View at shop: GO OutdoorsOsprey £30 In stock. Delivery £6. Black. Free shipping over £75; £6 delivery under that (Osprey UK delivery page, 'What are your delivery charges?').
View at shop: OspreyBlacks £26 Out of stock. Free delivery over £95.
View at shop: BlacksPrices 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
Waterproof build
Estimate from maker's specs: seams, closure and water rating 5/10How well its build keeps water out, from the published seams, closure and submersion claim. 5: Does the job. Average for wild-camping gear.
Estimate from maker's specs
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.
91 g for 36 L is 2.5 g/L, under 4.0 g/L. Osprey's UK page lists no weight, so the figure is from Osprey's US page (which lists it in US units, converted to 91 g). Shops give 87 g (Ultralight Outdoor Gear) and 100 g (Blacks and GO Outdoors), all under 4.0 g/L.
In short
Good for
- Waterproofing the inside of a 30 to 50 L rucksack with one light bag instead of several dry bags
- Rain protection on UK hill trips: unlike a pack cover, it needs no stopping to fit and isn't caught by wind
- Not for river crossings or anything that may go under water
Strengths
- 91 g for 36 L (2.5 g/L)
- Rectangular shape packs efficiently
- 100% recycled 40D high-tenacity nylon, bluesign approved
- Roll-top closure
- Sold by Osprey and several UK shops
Weaknesses
- Osprey describes waterproof-coated seams, not taped or welded ones
- Osprey sizes the Small for 30 to 50 L packs only
- Listed in one colour (Black) and one size
Sources
We haven't tested this ourselves. Every score comes from these specs, tests and reviews.