This rubber cover sits on the threshing unit of a combine harvester. It seals the gap between the rotating drum and the stationary concave housing, preventing crop material from escaping the threshing zone. A worn or torn cover allows grain and chaff to bypass the concave, reducing separation efficiency and increasing losses out the back of the machine. The cover is flexible enough to conform to the drum's curvature while maintaining contact under normal operating speeds. On replacement, ensure the mounting holes align with the existing studs and that the cover is not stretched or twisted during installation.