These handcuffs were designed for high risk transfers. Specially designed key and keyhole bushing. Smith & Wesson Handcuffs are fabricated from the finest quality carbon steel. They are manufactured with heat treated interrnal lockworks, featuring smooth ratchets for swift cuffing and double locks to prevent tampering. All S&W handcuffs meet or exceed demanding U. S. National Institute of Justice tests for workmanship, strength, corrosion and tamper resistance.