An exemplary lock apparatus includes a housing and a plug assembly rotatably mounted in the housing. The plug assembly includes a tumbler assembly operable to selectively prevent rotation of the plug assembly relative to the housing and a retention mechanism operable to selectively prevent removal of the plug assembly from the housing. A system including the lock apparatus may include a change key configured to actuate the tumbler assembly without actuating the retention mechanism and/or a control key configured to actuate both the tumbler assembly and the retention mechanism.