The RFI Modular Sleep System sleeping bags and other components are constructed to be used in conjunction with each other or separately to complete an interoperable system known as the extreme cold weather sleeping bag. The RFI sleep system is designed to provide comfort in temperatures ranging from 50°F to -50°F when wearing various layers of extreme cold weather clothing. This 5-Piece sleep kit is constructed to insulate the user in environments ranging from mild to extremely cold weather. It has been recorded to provide the user 4 hours of sleep in -40 degrees when both sleeping bags and bivy cover are used altogether. Includes: Two compression stuff sacks (one small and one large), two mummy style sleeping bags (patrol bag and intermediate cold weather bag, each made of water-resistant, rip-stop nylon)), ACU bivy cover .