Traditional Spark Plug, 12mm Thread Size, 19mm (3/4") Reach, 11/16" (18mm) Hex Size, Gasket Seat, Non-Resistor, Stud Terminal Threads, .028" (0.7mm) Gap, Heat Range 9. NOTE: Does not Include Terminal Nut, if necessary, order part #067606-0051 NGK traditional plugs are constructed for longer life and optimum performance. Corrugated ribs prevent flashover. NGK uses only the purest alumina silicate in its ceramic insulator which give all NGK plugs greater strength and better heat transfer. Copper cored and triple sealed to further aid in heat removal and prevent interior leakage.