The McCormick 3661935M1 is an authentic OEM flat washer, essential for various McCormick agricultural machinery, including X4.20, X4.30, X4.40, X5.35, X5.45, X5.55, and X5.65 series tractors. This precision-engineered washer, with an inner diameter of 10.5 mm, outer diameter of 20 mm, and thickness of 2 mm, ensures proper load distribution and secure fastening in critical applications. It is also an OEM equivalent for Massey Ferguson part number 3661935M1, fitting numerous MF 5400, 6400, 7400, and 8400 series models.