Champion Industrial Plug Number D18Y Spark Plug - 549 Part #: 549 Line: CHP Champion Industrial Plug Number D18Y Spark Plug 1 Year Limited Warranty Seat: Gasket Thread Size: M18 Heat Range: 18 Hex Size (mm): 22mm Hex Size (in): 7/8 Inch Preset Gap (in): 0.023 To 0.028 Inch Thread Reach (in): 0.500 Inch Resistor Plug: No Center Electrode Tip Material: Nickel Insulator Height (in): 0.060 Inch Ground Electrode Tip Material: Nickel Service Number: D18Y Metallurgy: Copper Show More Show Less