There are about 10 cylinders that make the top go up and down. If one is leaking you can replace that one and hope the others don't leak. However, most times if one is leaking the rest will leak after you fix the first one becuase of pressure build up. The cylinder you have to buy, my cost is $135 for the part. The front cylinders are 4-5inches and the ones in the back are 14-15inches. List is $775 for the back cylinders and I get 20% off at Benz as I'm sure you do being a car dealer. If we have a problem with one, we replace them all.