Wheel Hubcentric rings are designed to fill in the gap between the hub of the car and the center bore of the wheel. Most wheel manufacturers design their wheels with a centerbore large enough to fit on most cars. Therefore, since wheel manufactures make their center bore large enough to fit most cars, most wheel fitments have a gap between the hub and the centerbore. This gap usually doesn't allow for the wheel to fit hubcentric but rather lugcentric which causes vibration. Therefore, to fill the gap and ensure the fitment is hubcentric, hub rings are used.