One way clutch bearings to fit in the flywheel of most recumbent and upright bikes that require freewheel. 17mm x 35mm x 12mm. Will fit: Spirit, Horizon, Nordictrack, Proform, Weslo, Golds Gym, Epic, FreeMotion, Life Fitness, Sole and most other home recumbent and upright bike eddy mechanisms. This will stop the pedals from slipping.