Inconel with hard chrome finish. Standard size replacement with oversized head. Dimensions: 1.284" head dia. x 0.2342" stem dia. x 4.050" overall length. KPMI valves are manufactured in the U.S.A. by a dedicated staff and personnel with hands-on experience in stock and high performance. Quality materials and the latest CNC and 3-D computer modelling equipment make sure each and every Kibblewhite Precision Machining valve train component is top of the line. Inconel is a special heat resistant so-called ''Superalloy''. By nature of the material it cannot be black nitrided so it is hard chromed. It has a superior heat resistancy against issues like exhaust valve stem bending; of OEM M8 exhaust valves; without impact. 6mm is thin especially when dealing with extremities as detonation; lean mixtures and poor timing curves. Inconel''s superior heat resistance will maintain its strength longer at higher temperatures; it is therefore used for the thin stems on M8 exhaust valves only.