Autolite copper core spark plugs feature a cold-formed steel shell with precision-rolled threads, a full copper core electrode for better performance, and a one-piece terminal post to add strength. The ignition plugs use a copper-glass seal that bonds the insulator and terminal post center electrode together. This ensures full voltage at the spark gap and a 100 percent leak-proof, gas-tight seal. Autolite features an extensive application guide to cover just about everything with an internal combustion engine. Keep your engine running smoothly and reliably with Autolite replacement copper core spark plugs.