NGK Copper Plug Number BM6F Spark Plug - 6221 Part #: 6221 Line: NGK NGK Copper Plug Number BM6F Spark Plug 1 Year Limited Warranty Seat: Tapered Thread Size: M14-1.25 Heat Range: 6 Hex Size (mm): 16mm Hex Size (in): 5/8 Inch Preset Gap (in): 0.028 Inch Preset Gap (mm): 0.7mm Thread Reach (in): 0.375 Inch Resistor Plug: No Center Electrode Core Material: Copper Center Electrode Tip Material: Nickel Insulator Height (mm): 36.9mm Insulator Height (in): 1.450 Inch Ground Electrode Tip Material: Nickel Thread Reach (mm): 7.8mm Service Number: BM6F Metallurgy: Copper Show More Show Less