This rubber washer serves as the mounting gasket for the cab window glass on the host tractor. It sits between the glass edge and the cab frame, providing a sealed interface that prevents water and dust ingress into the cabin. The washer compresses evenly when the window is installed, maintaining consistent clamping force around the perimeter. A degraded or hardened gasket allows moisture to enter, which can lead to corrosion of the cab frame and fogging between glass layers. This original AGCO part is molded to the same profile as the original assembly, so it seats correctly in the frame channel without additional sealant. On reinstallation, ensure the glass is centered before tightening the retaining hardware.