There a basically 2 basic design versions in the freewheel (one way clutch) options. The Roller type feature a cylindrical outer race and inner race consisting of ramps on which the rollers are located. Springs and plungers ensure a permanent contact between the different elements for an instant torque transmissions. This rugged, reliable versatile design can be used as an overrunning clutch, indexing clutch or backstop. Worth noting: Stronger springs can be fitted to maximise accuracy in indexing applications.
The other design is the Sprag one. This type has 2 cylindrical races. The sprags (dogs) fitted into a cage feature an active profile that ensures engagement or disengagement according to the relative motion of the races. It is possible to adapt the design of sprags and cage to get significantly different characteristics from one model to another.