Stark's grey armor was the first Iron Man armor he made; it was built around an iron chest plate designed to prevent the piece of shrapnel he received in Vietnam from travelling to his heart and killing him. The armor, made from ordinary iron, provided protection from physical attacks, small arms, extreme temperatures, some forms of energy, and acid. Powered by flat linear armature rechargeable DC motors, the exoskeleton boosted the strength of the wearer by about 10 times, and employed motion-sensing negative feedback to control movement. Air pressure jets allowed for extended jumps and removable suction cups allowed the wearer to cling to walls and ceilings. Weaponry included a chest-mounted "monobeam" (proton beam generator), a miniature hacksaw, and magnetic turbo-insulators that allowed Stark to magnetically deflect metal projectiles or bring metal objects to him. Sensors consisted of a short-wave radio. All of the armor's devices and functions were manually controlled by the wearer. Stark used it to escape terrorists in Vietnam who were holding him hostage. He constructed at least one updated, form-fitting (although still rigid) version upon his return to the United States.