Military specifications. MIL-S-10899A. Semitrailer, chassis, 12-ton, 4W, M126, semitrailer, cargo, 12-ton, 4W, M127, semitrailer, cargo van, 12-ton, 4W, M128, semitrailer, gasoline tank, 12-ton, 4W, M121; Jan. 28, 1954.