The rotary locking cylinder comprises a housing (5) and at least one rotor (8) provided with a key channel (27). Tumblers are provided in order to rotationally release the armature (8) with a key (17) associated therewith. A driver (6) is provided with at least one extension element (3) on the active part (2) of the rotary cylinder. Said extension element comprises a housing (24) and a rotatable insert (9). At least one extension element (3) is arranged on an outer side on the active part (2) at a distance from the driver (6). The key shank is extended in a manner which corresponds substantially to the length (A) of the extension element (3). Preferably, the rotatable insert (9) of the extension element (3) is profiled.