This ring is a sealing and retaining component used in the hydraulic cylinder assembly of the cab system. It sits between the cylinder body and the piston rod, preventing fluid leakage and maintaining system pressure. A worn or damaged ring causes internal bypass, leading to slow or erratic cylinder movement. The manufacturer produces this ring to match the original groove dimensions, ensuring proper compression and sealing without the need for shimming or modification. On reinstallation, inspect the cylinder bore for scoring and replace the ring if any deformation is visible.