Plugs have a unique look with a black ceramic body and bold red logo/script. Insulator is made of 95% pure alumina, features strong resistance to heat shock and superior insulation. Multi-rib design of the insulator eliminates flashover. Nickel-plated housing prevents oxidation and corrosion. Multi-layer gaskets and heat crimping process ensure a leak-free, gas-tight seal. Copper core electrode prevents oxidation and corrosion, has good electrical and heat conductivity and creates long spark plug service life. Fits 99-17 Twincam, 86-22 XL (Except RH Sportster) models. Replace OEM 31600012. Sold in pairs.