Autolite Copper Core spark plugs 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. The multi-rib insulator reduces the danger of "flash-over" to prevent misfires, and the copper core center electrode provides higher thermal conductivity. These spark plugs are engineered with a high nickel alloy center and ground electrode for extended life.