With a polyester ripstop cover and polyester lining, it's designed to keep you warm from top to bottom while eliminating cold spots. The semi-sculpted hood surrounds your head, where most of your heat is lost, nice and warm. A special quilting construction eliminates the potential for cold spots to develop. The 3-in. insulated draft tube blocks heat loss through the zipper, while a box shaped foot gives you extra room to move your feet. When morning comes, the sleeping bag is easy to put away and store in the included stuff sack.