Eh; TSW site says, "All TSW alloy wheels offered are designed to be hub-centric which means that the load is transferred from the center of the wheel. This greatly improves the distribution of force while track driving. In some scenarios this will require a hub-centric ring."
I don't know what the red rings were in my box; they are gone now--guess they probably used them, or didn't.
Just curious what the other guys on here that have Nurbs did.