8-3/4 BBP Wheel Register Size?
The register is the diameter of the center of the axle (or hub center in front brakes), it fits snugly to the wheel and supports the majority of the weight (instead of the lugs) on the wheel/axle interface, and ensure that the wheel remains center true. This is known as "hub centric". Relying solely on the lug nuts/studs is known as "lug centric".
