Sea to Summit Altitude Women's Down Sleeping Bag 25

The Sea to Summit Altitude Women's Down Sleeping Bag 25 is the three-season entry in the women-specific Altitude line, tuned for milder conditions than its winter siblings. A comfort rating of -4°C and a limit of -10°C (EN ISO 23537) put it in spring, summer, and autumn territory where nights dip only modestly below freezing. The anatomical cut built for the female body — dead space removed, wider through the hips — carries over from the warmer models in the range, just with a thinner insulation layer: 520 g of 750-fill-power duck down, hydrophobic-treated and RDS-certified. The lighter fill keeps total weight to 1,080 g, and the warmth-to-weight figure (roughly 108 g per degree) reflects a lighter, less warm category of bag. A two-way zipper allows ventilation, and the 20D nylon shell keeps weight down. It is a typical warmth-versus-weight trade for hikers spending most of the season in milder weather without planning for genuinely cold nights.