Mountain Equipment
Mountain Equipment Helium 400 Down Sleeping Bag
Best use
- Made for
- Bikepacking, Backpacking and wild camping
- Not for
- Winter mountain
Why these labels
- Bikepacking: The maker states this use, and the published specs do not rule it out.
- Backpacking and wild camping: The maker states this use, and the published specs do not rule it out.
- Winter mountain: Comfort rating 0 °C: too cold for winter nights
From the maker's stated use and the published specs.
- Summer wild camp: 6/10 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: 8/10 How much it adds to your pack, compared with the whole market.
Comfort 0 °C, limit -6 °C (EN 13537).
Lowest price we found
£254.99 at Ultralight Outdoor Gear
Go to Ultralight Outdoor Gear Compare 3 shopsSpring and autumn UK hill camps, including nights near or just below freezing for warm sleepers
- Comfort
- 0 °C
- Limit
- -6 °C
- Fill
- 700 fill down
- Weight
- 820 g (Regular)
Packed size 10.1 L, 24 x 21 x 20 cm Compare with a 2-litre bottle
Shorter than a 2-litre bottle and about twice as wide. Drawn to scale.
Where to buy
Ultralight Outdoor Gear £254.99 In stock. Free delivery.
View at shop: Ultralight Outdoor GearEllis Brigham £300 In stock. Free delivery.
View at shop: Ellis BrighamMountain Equipment £300 In stock. Free delivery.
View at shop: Mountain EquipmentPrices 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
Warmth
From maker's figures 7/10How cold a night you can sleep comfortably through. 7: Better than most.
Maker's comfort 0 °C (limit -6 °C; its page labels the test EN13537/ISO23537) sits in the -4.9 to 0 °C band: good for spring and autumn with light frost. The maker's own 'Good Night's Sleep' figure is -5 °C.
Room inside
Estimate: only 1 review about room inside (fewer than the 3 we need, so never above 8) 4/10How much room to move, bend your knees and sleep on your side. Roomier is comfier. 4: A bit below average.
The one review calls the fit slim and athletic and says it won't suit everyone (2017 version; current Alpine Fit 2.0 is a little wider). The Helium GT 400 is the roomier option.
Weight
From maker's figures 8/10How much it adds to your pack. 8: Clearly better than most.
820 g (Regular) sits in the 700–999 g band.
Packed size
From maker's figures 4/10How much room it takes in your rucksack. 4: A bit below average.
Maker gives 24 x 21 x 20 cm: 24 x 21 x 20 = 10,080 cm³, so 10.1 L, in the 9–12.9 L band.
In short
Good for
- Spring and autumn UK hill camps, including nights near or just below freezing for warm sleepers
- Backpackers and cycle tourers who want a down bag under 850 g
Strengths
- 820 g with a maker comfort rating of 0 °C and limit of -6 °C
- Slanted box-wall baffles and a full-length zip baffle to cut cold spots
- Waterproof roll-top stuff sack included
- Shell and lining are 20D recycled nylon with a PFAS-free DWR finish
- Regular fits users up to 185 cm; a Long (200 cm) is 50 g heavier
Weaknesses
- Slim Alpine Fit: broad or restless sleepers may find it snug
- Packs to about 10 L, bigger than lighter-fill rivals
- Duck down at 700 fill power, with no stated water-repellent treatment on the down
- The 3/4-length zip is limiting if you want to put your feet out of the bag
- No independent hands-on review of the current version found, so damp, comfort and durability scores are Not enough evidence
Sources
We haven't tested this ourselves. Every score comes from these specs, tests and reviews.