This flat washer is used on the reel assembly of a combine header. It sits between a fastener and the reel component it secures, distributing the clamp load over a larger surface area to prevent localized deformation of the reel frame or bearing mount. A worn or missing washer can allow the fastener to loosen under vibration, leading to misalignment or damage to the reel drive components. The manufacturer machines this washer to the original thickness and hardness specification, which maintains the correct preload on the assembly without requiring shimming.