Champion RZ7C spark plug. Resistor plug, 10mm threads, 1/2" reach, 5/8" hex head. Champion  traditional plugs are constructed for longer life and optimum performance. Corrugated ribs prevent flashover. Champion  uses only the purest alumina silicate in its ceramic insulator which give all  plugs greater strength and better heat transfer. Copper cored and triple sealed to further aid in heat removal and prevent interior leakage.

To be used with most 20-  50cc engines