New to the spacer thing. I've heard the hubcentric spacers are much better for reduced vibration. The 66.2mm bore is for the load bearing part of the hub right?? I also assume this is the spacers' extruded flange outside diameter as well. If that's the case and I have aftermarket wheels w/ a fit bigger than 66.2mm will I run into problems? Are those hub rings needed for cases like this or should I be OK w/out them?
Thanks for any help w/ this

 

The rings ensure that your wheel stays centered on the hub when its tightened down. A non moving part that will eliminate vibration. Almost every aftermarket wheel uses hub rings. Instead of making an exact bore wheel for every car out there (which would make wheels thousands of $), they make a handful of the most popular bores and many ring sizes to make them fit the lesser common bore.

Not all rings are the same either. Some click in, some pressure fit, some need a retainer to hold onto. Best to contact the company that makes your wheels so you can get the proper ring.