4 New NGK Iridium IX Spark Plugs CR7HIX # 7544, Iridium IX Plug, 10mm Thread, 12.7mm (1/2") Reach, 5/8" (16mm) Hex Size, Gasket Seat, Resistor, Stud Terminal, Fine Wire (0.6mm) Iridium Center Electrode, Tapered Cut Ground Electrode, .027" (0.7mm) Gap, Heat Range 7. NOTE: Does not include terminal nut