This is a genuine OEM McCormick part number 3541443M1, identified as an oil filler cap or plug. It is designed to provide a secure seal for the oil fill point on engines or transmissions, preventing the ingress of contaminants and ensuring the proper functioning of the lubrication system. This essential component is also cross-compatible with a wide range of Massey Ferguson tractor models, making it a versatile replacement part for agricultural machinery maintenance.