crown international intake and exhaust valves are made from different materials to operate under different conditions. These are made from high grade valve steel series - en18d, en24, en52, en54, en59(214n) (non-magnetic/bimetal). Engine valves are also made with chrome plating for special purpose and are available in over sizes. The hardness of the valve series varies from 20hrc to 50hrc according to the material used and the application of the valve.