Description Reviews MINI Cooper S Piston Rings. Part No. 11-25-7-520-133 Brand New. Made by Perfect Circle, a very well known name in piston rings. Sold as a set of three rings for one piston. We can also get you rings for +25 over bore or Cooper's. Just give us a call. Keep in mind that it's not as easy as just installing new rings. You need to at least hone the cylinder correctly or machine the block cyl back into round by a machine shop. It all depends on your end goal and how good you want the outcome to be. More information can be found on the internet by doing a search. Reading up on this can save you a lot of time later. We offer rebuilding services also. Give us a call.