This O-ring seals a connection in the drive system of the parent combine. It sits between two mating surfaces to prevent hydraulic fluid or lubricant leakage under pressure. A degraded or hardened O-ring allows fluid to escape, which reduces system pressure and can lead to cavitation in the pump. The manufacturer specifies the cross-section and inner diameter to match the original seal groove, so the ring compresses to the correct fill ratio for a leak-free joint. On reinstallation, clean the groove and seat the ring evenly before tightening the mating flange.