Originally Posted by wstar

I think (from what I gathered there) that those are some kind of bolt-on adapters. Kinda like a spacer, that bolts into your lug holes and the provides the center-lock. Ideally for a race car, you'd actually replace the hub/bearing itself with a unit that was natively a single center lug (and then you'd need completely different brake rotor hats and wheels than stock). At least, luckily the hub/bearing thing on our car is separate from the arm it bolts to, so it wouldn't be too horrible to get this done.