Sea to Summit
Sea to Summit Trek -9 °C Down Sleeping Bag (Regular)
Where it fits
- Not for
- Winter mountain
Why these labels
- Winter mountain: Comfort rating -3 °C: too cold for winter nights
From the maker's stated use and the published specs.
- Summer wild camp: 5/10 UK, roughly May to September, nights above about 8 °C, sheltered pitches.
- Three-season hills: 6/10 UK hills in spring and autumn. Wind, rain, and nights near freezing.
- 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: 4/10 How much it adds to your pack, compared with the whole market.
Comfort -3 °C, limit -9 °C (ISO 23537).
Roomy, warm bag for spring and autumn camps and car-supported trips where weight matters less
- Comfort
- -3 °C
- Limit
- -9 °C
- Fill
- 650 fill down
- Weight
- 1.44 kg (Regular)
- Packed
- 10.6 L
Where to buy
Alpinetrek £240.77 In stock. Free delivery.
View at shop: AlpinetrekUltralight Outdoor Gear £314.99 In stock. Free delivery.
View at shop: Ultralight Outdoor GearSea to Summit £370 In stock. Free delivery. Free delivery over £75.
View at shop: Sea to SummitPrices checked 1 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 8/10How cold a night you can sleep comfortably through. 8: Clearly better than most.
Maker's ISO comfort rating is -3 °C (lower limit -9 °C), in the -4.9 to 0 °C band. The -9 in the name is the lower limit, not the comfort figure.
Room inside
Estimate from maker's specs: bag shape (fewer than 3 reviews about room) 5/10How much room to move, bend your knees and sleep on your side. Roomier is comfier. 5: Does the job. Average for wild-camping gear.
No review we found says how roomy it is, so this is an estimate from the bag shape.
Weight
From maker's figures 4/10How much it adds to your pack. 4: A bit below average.
1,436 g (Regular, maker's table) sits in the 1,300-1,699 g band. Ultralight Outdoor Gear lists 1,401 g.
Packed size
From maker's figures 4/10How much room it takes in your rucksack. 4: A bit below average.
Maker's compressed volume is 10.6 L, in the 9-12.9 L band. The supplied sack is a 20 L size, which is not the compressed volume.
In short
Good for
- Roomy, warm bag for spring and autumn camps and car-supported trips where weight matters less
- Side sleepers and restless sleepers who find mummy bags tight
- Cold-ish nights near 0 °C, with -3 °C ISO comfort
Strengths
- Roomy semi-rectangular cut with a full-length side zip and foot-box zip that let it open flat like a duvet
- -3 °C ISO comfort rating and -9 °C lower limit from a lab test
- 635 g of 650+ fill duck down gives plenty of warmth for the money, treated with Ultra-Dry Down
- Fitted draught collar, shaped hood and zip draught tubes
- Can take a Sea to Summit quilt over the top for extra warmth
Weaknesses
- Bulky at 10.6 L compressed
- 650 fill duck down is a low grade
- Roomy cut can feel too spacious for people who want a close, efficient fit
- 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.