This oil seal prevents hydraulic fluid leakage between the cylinder rod and the housing in the hydraulic cylinder of a self-loading forage trailer. It sits in the seal groove on the rod side of the cylinder, maintaining the pressure differential required for consistent cylinder extension and retraction. A worn or hardened seal allows fluid bypass, which leads to slow cylinder drift and reduced lifting capacity. The seal matches the original groove dimensions so no adapter or shimming is needed during replacement. On reinstall, ensure the seal lip faces the pressurized side of the cylinder and that the rod surface is free of scratches.