I have been seeing some leakage from my swing cylinder on the 4520A backhoe, so I decided to rebuild the cylinder. In preparation for the rebuild I ordered a seal kit #70030-01325 from Messicks for $136.58 delivered. I started the rebuild and found everything went well until I got to replacing the "O" rings that seal the end caps to the cylinder and found that the "O" ring supplied in the kit was about 3 1/4" instead of the 2 1/2" which would fit inside the cylinder. I called Messicks and they said all the kits they have in stock have the same wrong "O" ring. So, I called Kubota Customer Satisfaction line. They said they don't have the "O" ring part number and can't help me, even though they supplied the kit. So much for Kubota Customer Satisfaction. Be prepared to buy "O" rings to fit, if you decide to rebuild one of these cylinders. I ordered "O" rings from another source; hope they work.