I'm working on the unloading-auger swing-cylinder for the MF750 combine. It's a small diameter, so the ring has a very large relative stretch over the piston. The original ring was intact, but the auger would drift away from home. The replacement that I broke installing, held home initially, but now the auger drifts all over the place. It's gotten so bad you even have to help it along by hand. I ordered a new piston, but it comes without rings and seals. I hate to buy a new cylinder, as I know the rings are put on intact at the factory. I've had similar problems replacing the piston seals for many of my other farm equipment cylinders.