Autolite Copper Core spark plugs deliver quick starts, good fuel economy, and smooth acceleration. The copper-glass seal bonds insulator and terminal post center electrode together to ensure full required voltage at spark gap, creating a gas-tight seal that is 100 percent leak-proof. Copper Core spark plugs feature a cold-formed steel shell and precision rolled threads, and a one-piece terminal post that adds strength. The multi-rib insulator reduces the danger of "flash-over" to prevent misfires, and the resistor reduces radio frequency interference (RFI) and electrode erosion. The full copper core electrode provides better performance in all conditions. Autolite Copper Core plugs are your industry standard.