Designed to be used as a liner bag, inside another sleeping bag to add additional warmth, the 50F PrimaLiner can also be used as an ultra-light stand-alone sleeping bag. Weight and bulk are kept to a minimum with a contoured shape to fit the body, a snug fitting hood and a 15" zipper. Insulated with a single layer of 1.5in. 3oz Primaloft Sport and shelled with 1.1oz parachute ripstop nylon. The shaped foot box, and broad shoulder cut allow for differential layering during colder conditions and the freedom of movement in warmer summer conditions. The Primaliner adds about 15 C to a sleeping bag and has a stand-alone temperature rating of 50 F (10C).