CSK20 One-way Clutch Bearing 20mm x 47mm x 14mm CSK20 is a one-way clutch Ball bearing, One way Bearing Sprag/Clutch Freewheel and also called as Backstops, The one-way bearings are 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.