Sea to Summit Spark SpII -2°C £350

+ Incredibly light, 850 fill power, excellent for long-distance treks - Disappointing comfort rating, risk of down separating, low fill weight

This sleeping bag is designed for the gramcounting, ultralight camper who still needs 3-season protection. Top quality 850 fill power goose down (the highest grade down on test) fills both horizontal and vertical baffles, delivering an EN/ISO comfort rating of 4°C and comfort limit of -2°C for just 490g. That’s easily the lightest bag here – ideal for longdistance treks where every gram counts.

For colder nights, the 4°C rating won’t be warm enough, though we’re a little surprised by that grading as the super-lofty, plush down feels warm enough for nights a degree or two colder. Alternatively, if you need more warmth, the Spark SpIII has a comfort rating of -2°C, weighs 665g and costs £450.

Slight concerns with the SpII include the lightness of the 10-denier shell and 7-denier liner, which must be handled with care, and the potential risk of the down separating within the rather wide baffles or ‘leaking’ out of the stitched seams. But there are lots of positives too. You get a contoured mummy design, half-length YKK zipper with press stud closure at the collar, cinchable hood, water-repellent treatment to the down, and ‘zoned’ construction for more insulation in the vertical baffles across the torso.

■ Fill 300g of 850 fill power Ultra-Dry goose down ■ Temp rating 4°C comfort, -2°C comfort limit ■ Weight 490g ■ Pack size 25x15cm ■ Sizes Regular, long, women’s (Flame)

Verdict

An ultralight, minimalist down bag for gram-counting campers – but the comfort rating is a little disappointing.