centering ring .. if im correct .. is a plastic ring that goes on before the wheel / rim to stop it from being bolted on wrong, and decreases vibration .. thats what g-roads told me. i drove without them on my vw and it was so bumpy .. put them on.. $10 each so much better and put nitro fill in the tires makes it even smoother!
The centering ring allows the wheel to be centered on the hub so there are trye. If you don't use them you will have serious viberation problems. Use metal centering rings, plastic warp with heat transference. OZ rims ae excellent rims, Ferrari uses OZ on their F1 cars.
I have them on my Aero Looks nice. They are super light.. Just remember they are not tank wheels so be nice to them. Here are a couple images from and old autocross. Maybe I should wash it and take some pics.
I was also considering the 35th anniversary rims but they are just
way too heavy (28 ponds each). Other than that, the 35th should
look really nice on 93.
I also think the price of putting on the Ultraleggera will be an upgraded
brake kit latter on.