Melonite special black stem for Shovelhead 1966-later exhaust. Top quality U.S.A. made valves. Exhaust valves are made of 21-2N heat treated nonmagnetic stainless steel. Melonite black stem is a heat treating process developed and patented in Germany in the 1960's. Gives the valve a black smoky look. Very hard and slippery. Currently being used on OEM valves. Manufacturer