Designed for mountaineering, this cold-weather mummy bag features water-repellent down insulation, a waterproof/breathable shell and a double zipper system for temperature regulation.DetailsWith a temperature rating of -20°F, this bag is suitable for 4-season useUnique double zipper system allows you to adjust comfort as needed—fully close both zippers to increase warmth, open inner zipper to decrease warmthWater-repellent 700-fill-power duck down offers superior loft and warmthREI double-protection design combines a polymer-coated down fill with waterproof/breathable ripstop nylon all around; shell also has a durable water repellent finishREI in-the-round design puts vertical baffles in side walls to wrap you in warmth and create a better fit than bags that use only horizontal bafflesContoured hood, draft collar and full-length draft tubes all work to keep warmth inDifferentiated hood and neck drawcords simplify adjustments; antisnag zippers work smoothlyPass-through pocket has zippers on the outside and the inside to provide easy access to your stashed essentialsThe REI Expedition Sleeping Bag includes a nylon stuff sack and a large cotton storage bag