Cool. ... Wish I knew the Oring material they use. Im guessing EPDM. On my 2006 7520 that sits out 100%, the bucket cyl ring thats left is in perfect shape - no cracking. The other was scraped off apparently. I need some environmentally stable rings.Those o-rings (usually square cut) only serve to keep paint away from the cylinder rod's dust wiper located in the cylinder gland. Once the paint dries and the cylinder leaves the factory, the useful life of those o-rings is over and they are just along for the ride.