This washer sits between the baler plunger head and its retaining hardware, distributing clamp load across the bearing surface to prevent localized deformation of the casting. It is installed directly against the plunger face, where repeated impact loads from the compression cycle can otherwise cause the fastener to embed into the softer parent material. A worn or missing washer allows the bolt head to loosen during operation, leading to plunger misalignment and increased shear stress on the connecting rod. The original geometry matches the counterbore depth and bolt shoulder height of the assembly, so no shimming or spacer stacking is required during replacement. On reinstall, ensure the washer is seated flat against the plunger face before torquing the retaining fastener.