NGK's standard plugs are constructed for longer life and optimum performance with corrugated ribs and a triple-gasket sealing process.Copper core14mm thread size, 1.25mm thread pitch shell2.5mm standard nickel projected centre electrodeStandard nickel ground electrodeTrivalent metal plating provides superior anti-corrosion and anti-seizing propertiesCorrugated ribs prevent flashoverPure alumina silicate ceramic insulator, provides superior strength and better heat transferCopper core aids in heat removalTriple seals prevent leakage