Hubcenric Rings...
 

Do i need these for my rims?

They are volk gramlight 57c's, and going on my 90 s5 n/a

Not sure what they do really

There was an interesting discussion on this subject in the wheels and tires section a month ago or so:

https://www.rx7club.com/showthread.p...ighlight=rings

Yes you do!! Get a set from Discount Tire Direct. They sell them on Ebay. Just do a search on hubcentric rings and you'll find them. They're only $10 shipped or so. I got mine from them and it's very high quality. Read the link david provided... and you'll understand what they do.