The McCormick 3663917M1 is a genuine OEM lock washer designed to provide secure fastening and prevent loosening in agricultural machinery. This essential component is compatible with a wide range of McCormick X-series tractors, including models X4.20, X4.30, X4.40, X4.50, X5.35, X5.45, X5.55, X6.420, X6.430, X6.440, X7.440, X7.450, X7.460, X7.650, X7.660, X7.670, X7.680, X8.660, X8.670, X8.680, and X8.690. Manufactured to McCormick's stringent quality standards, it ensures reliable performance and durability in demanding operational conditions.