4 New NGK IRIDIUM IX Spark Plug LTR5IX-11 # 4344, Iridium IX Plug, 14mm Thread Size, 25mm (.984") Reach, 5/8" (16mm) Hex Size, Tapered Seat, Resistor, Projected Tip, Solid Terminal Nut, Fine Wire (0.6mm) Iridium Center Electrode, Tapered Cut Ground Electrode, .043" (1.1mm) Gap, Heat Range 5