M-970 Semitrailer, Tank, Fuel Dispensing, 5,000 Gal. Under/Over Wing Aircraft, manufactured by Heil Company in 2007. Huntsville, AL, September 2012. Courtesy: Government Liquidation LLC.
Military vehicle semitrailers for fuel and water have a tank mounted on a chassis. Since the word tank is ambigious, these semitrailers must be distinguished from trailers whose purpose is to carry or retrieve armored vehicles (e.g. M4 Sherman tank).