AS40 One Way Clutch One Clutch AS40 is a one-way clutch, that is used for Overrunning, Indexing and Backstopping, this type is non-bearing supported, you will need one of the 6205 beairngs to support it, One way Bearing Sprag/Clutch Freewheel and also called as Backstops. AS40 is used in any application that requires one direction rotation, such as mining, hydraulic, textile, printing and washing machines, conveyor systems that carry products to a higher level should not be reversed because of gravity during any power shortage.