Most aftermarket wheels are manufactured with a center hole that will fit a wide range of vehicles. The hub-centric ring is used to fill any gap that may exist between this hole and the vehicle's hub, thus centering the wheel on the axle. If you have vibrations after installing new wheels, chances are hub-centric rings were not used.

This term is used to refer to the physical specifications of the wheel and the availability of the sizes that will fit a vehicle. So, the fitment specifications for a particular wheel and vehicle include the bolt pattern, the offset, the wheel width and the wheel diameter.