The 36.6 mm exhaust valve seat with part number 1-05996 serves as a high-precision sealing and contact surface for the exhaust valve in the BMW Isetta engine, ensuring compression and heat dissipation. During an engine overhaul, the worn seat is removed, the new valve seat is pressed in, and the valve seat surface is precisely reworked to restore sealing and clean gas exchange. This is particularly important for restored Isetta engines to permanently prevent power loss and valve damage.