This exhaust valve seat is the component that seals the exhaust port against the cylinder head during the valve-closed portion of the four-stroke cycle. It is pressed into the cylinder head and provides the stationary sealing surface that the exhaust valve face contacts. A worn or recessed seat reduces compression and allows exhaust gas leakage, which degrades engine power and can lead to valve burning. As an original-manufacturer part from AGCO, the seat is machined to the same interference fit and concentricity tolerance as the original assembly, so no reaming or lapping is required beyond standard valve-seat preparation. On installation, ensure the seat is fully seated in the counterbore and that the valve guide is clean before final assembly.