Warmth whenever and wherever you need it! This extra large, breathable and easy-care 3-season synthetic fill mummy sleeping bag is also environmentally sustainable, made with bluesign certified materials. The Sensofiber micro-fiber fill reflects body heat yet efficiently transfers moisture away from the body and so maintains a wonderfully comfortable sleeping climate. As all synthetic fibers, Sensofiber warms even when damp, is quick drying, easy to maintain and long-lasting. The Sioux 800 XL is a solidly reliable, warm outdoor sleeping bag for trekking and cabin tours.