Check the listing for details. GI US Military 5 Piece Improved Modular Sleep System (IMSS) ACU. Condition: New with tags. Listed at 274.99 USD. The US Military Improved 5-Part ACU Digital Sleep System is a sleeping bag system constructed to insulate the user in environments ranging from mild weather to extremely cold weather. The system consists of two Mummy-style sleeping bags--the Patrol (Foliage) and the Intermediate Cold Weather (Urban Grey). Each are constructed of water-resistant, ripstop nylon. Each sleeping bag is fully functional independently. For a temperature to -30°, insert the Intermediate Cold Weather bag inside the Patrol bag. Each bag is compatible with the vapor permeable bivy cover. When all 3 components are used together the system is rated to provide 4 hours sleep at -40°F. This 5-part system includes a second smaller stuff sack. Non-flammable and machine washable.