This o-ring seals the connection between the hydraulic system and the rear three-point linkage on the host tractor. It sits in a groove at the interface, preventing fluid leakage that would reduce lift capacity and introduce air into the circuit. A degraded or flattened o-ring causes slow hitch response and visible oil seepage at the joint. The part is manufactured by AGCO to the same cross-section and inner diameter as the original seal, so it seats fully in the groove without requiring shimming or adapters. On reinstall, ensure the sealing surfaces are clean and free of burrs before fitting the new ring.