Formsprag requires that all clutches and holdbacks be axially restrained when mounted . Our recommended bore to shaft fits are loose to facilitate installation and removal, therefore, axial restraint must be provided by set collars, shoulders, restraining keys, retaining snap rings, retainer plates, or some other axial restraint device approved by Formsprag . Holdback axial restraint is required to prevent the reaction end of the torque arm from imposing biasing loads on the bearings . Holdbacks installed without axial restraint can shift on the shaft, causing bearing loads which can significantly reduce bearing B-10 life . For customers wishing to have a tolerance gap between the axial restraining device and the holdback inner race, a maximum gap of 1/8” per side is recommended.