ACDelco Copper Spark Plug - 25186682 Part #: 25186682 Line: ACD ACDelco Copper Spark Plug 12 Month Or 12,000 Mile Limited Warranty Seat: Gasket Thread Size: M14 Hex Size (mm): 16mm Hex Size (in): 5/8 Inch Preset Gap (in): 0.039 Inch Preset Gap (mm): 1mm Thread Reach (in): 0.750 Inch Resistor Plug: Yes Center Electrode Core Material: Copper Center Electrode Tip Material: Copper Ground Electrode Tip Material: Nickel Thread Reach (mm): 19mm Metallurgy: Copper Show More Show Less