This U.S. Military APCES (All-Purpose Environmental Clothing System) Trouser Liner represents the modern evolution of the legendary ECWCS (Extended Cold Weather Clothing System). This is the same protective outer layer worn by Air Force and USMC personnel to deal with extreme cold weather and inclement conditions. Heat-regulating heavyweight polyester fleece. Treated with a DWR water-resistant coating against rain and snow. Designed with extra room to go over the top of regular pants.