GMN rings are made of hardened and ground ball bearing steel. The FPD, FND, RA, FP and FN series of complete freewheel clutch units, the FK (2RS), FKN (2RS) and FKNN (2RS) series of ball bearing freewheel clutches and the FR and FRN series of freewheel clutch insert elements have rings.

Press fit connection

The modest wall thickness of rings for press fit connections (2–2.5 mm) permits installation in limited spaces. These thin-wall rings are designed to take on the desired start gap height (h0) only after the rings are pressed in or on (steel connecting parts; for tolerances, see size tables). A press fit connection ensures the greatest possible torque transfer.

Press fit connection 

Keyway connection

All GMN rings with a keyway are designed for easy push-on seating that supports torque transfer. A keyway connection alone is insufficient for the transfer of nominal torque.


Series with rings:

  • Freewheel insert elements with rings: all series
  • Ball bearing freewheel clutches: all series
  • Complete freewheel clutch units: all series


  • Material: 100 Cr6 (material number 1.3505)
  • Hardness: HRC 60+4 (HV 700+100)
  • Surface: Rz ≤ 2.5 μm (Ra ≤ 0.4)