This seal ring fits into the groove of a hydraulic cylinder rod or piston to prevent fluid leakage past the dynamic seal interface. It sits between the cylinder barrel and the moving element, maintaining a pressurized seal during extension and retraction cycles. A worn or damaged seal ring allows internal bypass, which reduces cylinder holding force and causes drift under load. The original part is machined to match the groove dimensions of the cylinder assembly, ensuring the seal is compressed to the correct interference for the operating pressure range. On installation, inspect the groove for burrs or debris and lubricate the ring before assembly.