Ngk traditional plugs are constructed for longer life and optimum performance. Corrugated ribs prevent flash over. 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. The bp6es is one range colder than the bp5es and are for more spirited driving. Sold each, four needed per car.