NGK Standard Spark Plugs are treated with corrosion resistant plating to ensure ease of installation and removal. The 98% pure copper core delivers increased heat dissipation for more reliable starts and reduced risk of overheating. Cold-rolled threads prevent cross-threading and damage to cylinder heads. Trivalent plating eliminates need for anti-seize. Corrugated ribs prevent flashover. High-grade alumina silicate ceramic. Iridium enables an especially narrow middle electrode, with a diameter of only 0.6 mm.