This washer is installed on the threshing drum assembly of the parent forage harvester or combine. It functions as a precision spacer between rotating components, maintaining the correct axial clearance on the drum shaft. A worn or missing washer allows the drum to shift on its shaft, causing vibration and uneven wear on adjacent bearings and seals. This original part is manufactured to the same thickness and bore tolerance as the component it replaces, so no shimming or additional adjustment is needed during installation.