These valves are made from stainless steel and feature a Stellite tip and seating surface. Stellite is an extremely hard cobalt-chromium alloy developed for wear and corrosion resistance. The Stellite helps the valves resist valve stem tip wear and deformation as well as damage to the seating surface from wear and hot exhaust gases.
1.255 inches is the original exhaust valve size for the TR250, the 1969-1972 GT6 Mk 2-3 and the TR6 up to engine #CF/CR1. 1.255 inch exhaust valves may be used in later heads by enlarging the seating surface.