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Sea to Summit

Sea to Summit Ultra-Sil Dry Bag (20 L)

Mid Confidence: High
  • 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.

Lowest price we found

£15.99 at Ultralight Outdoor Gear

In stock. Free delivery. Checked 8 Nov 2026.

RRP £28, checked 19 Oct 2026.

Go to Ultralight Outdoor Gear Compare 2 shops

Protecting a sleeping bag, down jacket or spare clothes inside a rucksack

Capacity
20 L
Weight
58 g
Seams
Taped
Closure
Roll top
Fabric
30 denier

Where to buy

Ultralight Outdoor Gear £15.99 In stock. Free delivery. Free UK delivery over £15.

View at shop

Sea to Summit £28 In stock. Delivery £4.50. Free delivery over £75.

View at shop

Prices 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

From maker's figures 6/10

How well its build keeps water out, from the published seams, closure and submersion claim. 6: A bit better than average.

Taped seams and a hypalon roll-top. Sea to Summit says it is waterproof where the bag will not be submerged and meant for use inside a pack, so there is no submersion claim: the 3 band.

Weight for its size

From maker's figures 10/10

How much it adds to your pack for the space it protects. 10: The best you can buy for this.

58 g for 20 L is 2.9 g/L, under 4.0 g/L (Sea to Summit's figure; Ultralight Outdoor Gear lists 56 g, the same band).

In short

Good for

  • Protecting a sleeping bag, down jacket or spare clothes inside a rucksack
  • Ultralight kits where every gram counts: 58 g for 20 L
  • Use inside a pack, not strapped outside or for paddling

Strengths

  • Very light: 58 g for 20 L (2.9 g/L)
  • Translucent 30D Ultra-Sil fabric with Cordura yarns, so you can see what is inside
  • Slippery finish for easy packing and unpacking
  • Taped seams and a hypalon roll-top closure
  • Oval base stops it rolling away and packs efficiently

Weaknesses

  • Thin 30D fabric, meant for inside a pack rather than rough outside use
  • Not submersible: Sea to Summit says to use it where the bag will not be under water
  • No reviews of the 20 L itself were found, so durability and ease scores are missing

Sources

We haven't tested this ourselves. Every score comes from these specs, tests and reviews.

ShowHide sources (5)
  1. Sea to Summit UK: Ultra-Sil Dry Bag, 20 L size table Specs, 19 Oct 2026. Used for: waterproof build, weight for its size
  2. The Great Outdoors: Three of the best dry bags for hiking, Ultra-Sil (13 L tested; not used for a score) Review, 21 Jun 2022
  3. OutdoorGearLab: The Best Dry Bags, Ultra-Sil set of 3 (3, 5 and 8 L tested; not used for a score) Test, 16 Sept 2025
  4. Backcountry Magazine: Sea to Summit stuff sacks and packing systems reviewed (no size given; not used for a score) Review, 19 Sept 2023
  5. Sea to Summit UK customer reviews: Ultra-Sil Dry Bag (102 reviews, 4.8 out of 5, all sizes; not used for a score) Shop customer reviews, 19 Oct 2026