For Russwin/Corbin heavy duty and CL-3400 standard duty knobs. This product has ABLOY PROTEC²-lock system. ABLOY PROTEC²is a factory level locking solution. Every key is carefully controlled and is only made at Abloy Oy's factory. The keys have a patented sliding element that increases key security. One key fits several locks. How many locks a single key opens and who has access to what, can be accurately controlled. Available with multiple different surface treatments.