An interchangeable core aka I-Core is a small, self-contained lock cylinder, usually "figure-eight" in shape, that can be extracted from its housing via a special "control key".
It is designed to fit into a variety of cylinder housings that comply with its size specifications through standardization, and produced by a variety of lock manufacturers.
Interchangeable cores are very popular within commercial, institutional, industrial and government facilities.
Interchangeable cores can be removed from one type of lock bored cylindrical lock, mortise lock, padlock, etc. and placed into another lock without need of dismantling or removal of the lock cylinder or lock.