Chicago handcuff company manufacturers high quality police handcuffs. The model 1000 is constructed of nickel-plated steel. Nickel plating protects handcuffs from rust & gives them a nice shiny finish for a professional presentation. Chicago handcuffs utilize a push pin double locking mechanism. The double lock functions identical to Peerless handcuffs. To double lock, simply depress the double lock pin located on the edge of the cuff with the pin on your handcuff key. These handcuffs open with a standard key (2 included). Stamped CHICAGO on both cuffs. These have 22 locking positions, an inner perimeter of 5 5/8" to 8 1/4" and weigh 9.4 ounces. Excellent value for professional quality handcuffs. Chicago handcuffs have a lifetime warranty against manufacturer defects.