CDU (Continuous Drive Unit) Series Overrunning Clutches are designed to be robust for the most difficult applications. CDU Series Overrunning Clutches are intended for use in continuous overrunning applications where the system cannot be shut down for maintenance and for applications in extremely harsh and dusty environments such as coal handling systems. A CDU consists of an FSO overrunning, sprag clutch installed in a foot-mounted housing which encloses a generous supply of oil.