Inner rings are used where:
The shaft cannot be used as a rolling bearing raceway for needle roller and cage assemblies, drawn cup needle roller bearings with open ends, drawn cup needle roller bearings with closed end and needle roller bearings (it cannot be hardened and ground)
Needle roller bearings must be combined with wider inner rings in order to allow larger axial displacements of the shaft in relation to the housing (e.g. in bearings with a non-locating bearing function)
Optimum running surfaces are required for seal lips