AS20 One Way Clutch Bearing One Clutch AS20 = NSS20 AS20 is a one-way clutchthat is used for Overrunning, Indexing and Backstopping, this type is non-bearing supported, this is exactly the same size as any 6204 ball bearing, you will need one of the 6204 beairngs to support it, One way Bearing Sprag/Clutch Freewheel and also called as Backstops. AS20 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.