Marmot Helium 15

The Marmot Helium 15 is a mummy-shaped down sleeping bag built for 3-season backpacking and mountaineering, where weight matters but temperatures can still drop well below freezing. RDS-certified 850-fill-power goose down at a 90/10 down-to-feather ratio, plus a hydrophobic down treatment, gives it a strong warmth-to-weight ratio: at 980 g total weight with 552 g of fill, it carries an EN comfort rating of -2°C, a -9°C limit, and a -27°C extreme figure — numbers aimed at shoulder-season and alpine use rather than summer trips. The Pertex Quantum 20D shell keeps weight down while adding wind and moisture resistance a bare down shell would lack, and horizontal box-baffle construction limits down shifting better than sewn-through seams. A full-length, two-way zipper allows venting on milder nights without sacrificing the mummy cut's warmth. Sized for users up to 183 cm in a men's-specific fit, it suits solo thru-hikers and alpinists who prioritize low pack weight over the extra room of a wider bag.