The McCormick 399778R1 is a genuine OEM flat washer designed for various International Harvester tractor models. This essential component provides a secure and stable seating surface for fasteners, distributing load and preventing loosening due to vibration. With an inner diameter of 26.9875 mm, an outer diameter of 47.625 mm, and a thickness of 3.175 mm, it ensures precise fitment and reliable performance in demanding agricultural applications. It is also cross-referenced as Case IH 399778R1.