These bit keys are constructed of diecast and come in a zinc plated finish. These keys (also known as Skeleton Keys) are manufactured with up to 3 bits, a stop collar and key number on each, and are packaged in quantities of 4 keys per pack. The vintage mortise lock sets and surface mount lock sets that these keys are compatible with are those manufactured by Prime-Line Products, which are designed for interior use only. This key has a ward cut on the left-hand side of bit when facing the keyhole.