NGK standard plugs are constructed for longer life and optimum performance. Trivalent metal plating provides superior anti-corrosion and anti-seizing properties. Corrugated ribs prevent flashover. Pure alumina silicate ceramic insulator, provides superior strength and better heat transfer. Copper core aids in heat removal. Triple seals prevent leakage. Thread Size: 14mm. Thread Pitch: 1. 25mm. Seat Type: Gasket. Resistor Value: 5K Ohm. Reach: 19mm (3/4"). Hex Size: 13/16" (21mm). Terminal Type: Solid. Overall Height: JIS. Gap: . 031" (0. 8mm). Material: Nickel. Type: Standard. Size: 2. 5mm. Projection: Projected.