Weather protection for winter: lightweight bivy sack that packs down small made of waterproof, bluesign® certified material. Provides good weather protection thanks to the contoured mummy design, hood and drawstring. This bivy sack can both be used outside a sleeping bag (protection against snow, rain and wind) as well as a vapor barrier inside the bag on winter tours. This prevents the dew point from moving into the sleeping bag in cold temperatures and causing the down to lose its insulation properties.