4 New NGK IRIDIUM IX Spark Plugs UR6IX # 7348, Iridium IX Plug, 14mm Thread Size, 11mm (7/16") Reach, 5/8" (16mm) Hex Size, Tapered Seat, Resistor, Solid Terminal Nut, Projected Tip, Fine Wire (0.6mm) Iridium Center Electrode, Tapered Cut Ground Electrode, .040" (1.02mm) Gap, Heat Range 6