This seal ring sits in the piston rod gland of a hydraulic cylinder. It prevents pressurized fluid from leaking past the rod during extension and retraction cycles. A worn or damaged seal ring causes external oil leakage, reduces cylinder holding force, and can allow contamination to enter the hydraulic circuit. The ring is molded to match the original groove geometry so it seats correctly against the rod surface without requiring additional shimming or adapters. On installation, lubricate the seal and the rod before assembly to avoid rolling or pinching the ring.