NEMO Sonic™ Down Mummy Sleeping Bag -20

The NEMO Sonic -20 is a dedicated cold-weather expedition bag, rated by the manufacturer to a comfort of -20°C, a limit of -29°C, and an extreme rating of -35°C - firmly in five-season territory for winter mountaineering or high-altitude use rather than typical three-season backpacking. It carries 1060 g of 800-fill-power hydrophobic goose down (RDS-certified) in horizontal box baffles inside a 20D recycled nylon ripstop shell, giving a warmth-to-weight ratio of 16.5 and around 61 g of bag weight per degree of comfort, reflecting how much of the 1760 g total goes directly into insulation rather than hardware. Features built for serious cold include a fitted contoured hood, both a draft collar and draft tube, and a waterproof Toester footbox that resists moisture where condensation and tent-floor contact are worst. The 100% recycled, bluesign-certified fabrics and PFC-free treatment address environmental impact without a performance compromise. Fits users up to 182 cm. This is a specialist bag for genuine winter conditions, not a general-purpose three-season choice - its weight and bulk would be excessive for milder trips.