ACDelco Professional Iridium Spark Plug - 41-988 Part #: 41-988 Line: ACD ACDelco Professional Iridium Spark Plug 7 Year Limited Warranty Seat: Tapered Thread Size: M14-1.25 Heat Range: 12 Hex Size (mm): 16mm Hex Size (in): 5/8 Inch Preset Gap (in): 0.047 Inch Preset Gap (mm): 1.2mm Thread Reach (in): 0.980 Inch Resistor Plug: Yes Center Electrode Core Material: Copper Center Electrode Tip Material: Iridium Approximate Resistor Value (Ohm): 3000 To 10000 Ohm Insulator Height (mm): 50.5mm Insulator Height (in): 1.988 Inch Ground Electrode Tip Material: Nickel Thread Reach (mm): 25mm Metallurgy: Iridium Show More Show Less