Sea to Summit
Sea to Summit Ascent -1 °C Down Sleeping Bag (Regular)
Best use
- Made for
- Backpacking and wild camping
- Also works for
- Bikepacking
- Not for
- Winter mountain
Why these labels
- Backpacking and wild camping: The maker states this use, and the published specs do not rule it out.
- Bikepacking: Small enough for bike bags: packs to 5.5 litres
- Winter mountain: Comfort rating 3 °C: too cold for winter nights
From the maker's stated use and the published specs.
- Summer wild camp: 7/10 UK, roughly May to September, nights above about 8 °C, sheltered pitches.
- Three-season hills: 4/10 UK hills in spring and autumn. Wind, rain, and nights near freezing. Capped at 4: needs warmth 7+ (comfort 0 °C or colder).
- Winter camp: 4/10 UK winter or high ground. Below freezing, strong wind, possibly snow. Capped at 4: needs warmth 9+ (comfort -5 °C or colder).
- Weight: 8/10 How much it adds to your pack, compared with the whole market.
Comfort 3 °C, limit -1 °C (ISO 23537).
Three-season wild camps in the UK from spring to autumn, with nights just above freezing
- Zip side
- Both
- Comfort
- 3 °C
- Limit
- -1 °C
- Fill
- 750 fill down
- Weight
- 782 g (Regular)
- Packed
- 5.5 L
Where to buy
Cotswold Outdoor £299.95 In stock. Free delivery.
View at shop: Cotswold OutdoorSea to Summit £375 In stock. Free delivery. Free delivery over £75.
View at shop: Sea to SummitUltralight Outdoor Gear £299.99 Out of stock. Regular out of stock on 2 Nov 2026 (the Long is in stock at £319.99).
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
Warmth
From maker's figures 5/10How cold a night you can sleep comfortably through. 5: Does the job. Average for wild-camping gear.
Maker's ISO comfort rating is 3 °C (lower limit -1 °C), in the 0.1 to 5 °C band. The -1 in the name is the lower limit. One review quotes 4 °C comfort, which is not the maker's figure.
Room inside
Estimate: only 1 review about room inside (fewer than the 3 we need, so never above 8) 8/10How much room to move, bend your knees and sleep on your side. Roomier is comfier. 8: Clearly better than most.
One reviewer found the relaxed mummy cut roomy enough to sleep on your side, with extra space at the knees and shoulders.
Weight
From maker's figures 8/10How much it adds to your pack. 8: Clearly better than most.
782 g (Regular, maker's table) sits in the 700-999 g band. Ultralight Outdoor Gear lists 777 g.
Packed size
From maker's figures 7/10How much room it takes in your rucksack. 7: Better than most.
Maker's compressed volume is 5.5 L, in the 4-5.9 L band. The supplied compression sack is an 8 L size, which is not the compressed volume.
In short
Good for
- Three-season wild camps in the UK from spring to autumn, with nights just above freezing
- Fastpacking and bikepacking where a 782 g bag that packs to 5.5 L matters
- Bivvy and tent campers who meet condensation (hydrophobic down)
Strengths
- 782 g and 5.5 L compressed for a bag with a 3 °C ISO comfort rating and -1 °C lower limit
- 750+ fill goose down with Ultra-Dry Down water-repellent treatment
- Free Flow zip system: full-length side zip, half-length zip on the other side and a foot-box zip, so it opens out into a quilt on warm nights
- Relaxed mummy fit with room in the hood for a pillow and an internal pocket
- Shell has a non-PFAS water-repellent finish against wind and moisture (maker's claim)
Weaknesses
- Comfort rating is only 3 °C: for sub-zero nights it needs a warmer bag or layers
- 20 denier shell is thin, so it needs care on rough ground
- Supplied compression sack is not waterproof, so use a dry bag in heavy rain (Great British Adventure Club)
- Only one independent review of this exact bag found, so damp, comfort and durability are estimates, not reviewed scores
Sources
We haven't tested this ourselves. Every score comes from these specs, tests and reviews.