MIL-S-55541G, MILITARY SPECIFICATION: SHELTER, ELECTRICAL, SHELTER, S-250 ( )/G (01 AUG 1984) [NO S/S DOCUMENT]., This specification covers one type of lightweight field and mobile shelter designed for transport by cargo truck, fixed or rotary winged aircraft, rail and ship, and designated Shelter, Electrical Equipment, S-250( )/G (See 6.2).