4 New NGK IRIDIUM IX Spark Plug CR7EIX # 7385, Iridium IX Plug, 10mm Thread Size, 19mm (3/4") Reach, 5/8" (16mm) Hex Size, Gasket Seat, Resistor, Stud Terminal Threads, Fine Wire (0.6mm) Iridium Center Electrode, Tapered Cut Ground Electrode, .031" (0.8mm) Gap, Heat Range 7. NOTE: Does not Include Terminal Nut