Small Format Interchangeable Core, also known as SFIC, is an easy way to change who has access to rooms by changing the cylinder inside the locking device. Small Format Interchangeable Core is an ideal system for commercial use. This a specialty service so not all locksmiths can provide this service for you.
The way the system works is two key minimum. One of the keys is called a core key. The core key allows you to remove the core(cylinder) from the lock. The other key operates the lock like a normal key. The core key cannot unlock the door, it is only used to remove the core. Master key system is available for SFIC as well. For more information on that click here. Similar to the master key system, you can have multiple keys work a cylinder. With this level of a system, you can have a key for managers, owner, staff and more. Having restrictions to who can open which door.