This seal ring fits the piston rod or gland of a hydraulic cylinder on a self-propelled forage harvester. It sits in the annular groove between the cylinder barrel and the rod, preventing pressurized oil from leaking past the rod seal. A worn or hardened seal ring causes external oil leakage, reduced cylinder holding force, and slower implement response. The manufacturer machines the seal to the same cross-section and hardness as the original, so it seats correctly in the groove without requiring shims or adapters. On installation, clean the groove thoroughly and lubricate the seal before assembly.