Autolite Copper Resistor Spark Plug deliver quick starts good fuel economy and smooth acceleration. The copper-glass seal bonded insulator terminal post and center electrode ensure a tight seal that is 100 percent leak-proof and the full copper core electrode improves heat transfer and optimizes plug life. Copper Core spark plugs feature high alumina ceramic for high dielectric strength and a steel shell for installation robustness. These spark plugs are engineered with a high nickel alloy center and ground electrode for extended life.