NFS40 One Way Clutch 40mm x 90mm x 33mm NFS40 is a one-way clutch, One way Sprag/Clutch Freewheel and also called as Backstops, NFS40 is used in any applications 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.