These are heavy duty stainless steel wrist cuffs. They lock in place with integrated screw locks. They are made of solid high quality heavy stainless steel polished to a mirror finish. They have the feel and security of the real prison cuffs in a clean esthetic pleasing quality and without the grunge. A detachable polished connecting link in included. The Cuff inside diameter is 2 1/3 inches (6cm). Unisex style and use.