3678603 heavy-duty O-ring is customized for Cummins ISX, QSX and X15 engines working in harsh environments. The special rubber formula enhances vibration resistance and corrosion resistance against various engine fluids. It maintains stable sealing effect under long-time shock and temperature change. Accurate size fits original grooves perfectly for quick installation. It is a practical consumable part for mining, construction and other heavy equipment engine repair.