The McCormick 6639981A1 duct is an authentic OEM component designed for various McCormick X4 series tractor models, including X4.20, X4.30, X4.40, X4.50, X4.60, X4.20M, X4.30M, X4.40M, X4.50M, X4.20F, X4.30F, X4.40F, X4.50F, X4.60F, X4.20V, X4.30V, X4.40V, X4.50V, X4.60V, X4.35, X4.45, X4.55, X4.35M, X4.45M, X4.55M, X4.35F, X4.45F, X4.55F, X4.35V, X4.45V, and X4.55V. This duct ensures correct airflow within the machine's systems, maintaining optimal performance and preventing issues caused by improper ventilation.