Sea To Summit Alpine -29°C is a mummy sleeping bag designed to keep you warm even in the harshest conditions. Designed down to the smallest detail, Alpine is filled with RDS down and treated with the eco-friendly Ultra-Dry Down treatment to offer maximum performance even in wet and humid conditions. In addition, its filling has a filling power of 850+, which means that one ounce (30 g) of down will expand by more than 850 cubic inches after compression. A higher filling power means that less down can be used to achieve the same temperature, which is important for high-performance sleeping bags. The details are researched and tested over the years: expedition mummy shape to accommodate gear inside that you don't want to leave outside, hood with collar to keep heat out that can accommodate a pillow, zip closure on one side (mates with all Sea To Summit women's models) with an additional zip covering 1/3 of the length to regulate internal ventilation. Sea To Summit Alpine -29°C expedition sleeping bag