Spark Plug Application Commercial and Industrial Lawn and Garden Hex Size 5/8 in Thread Size 0.393 in Thread Reach 0.375 in Ground Electrode Quantity 1 Ground Electrode Tip Design Standard Gap Size 0.028 in Resistor Plug Yes Hex Size - Metric 15.88 mm Thread Reach - Metric 9.6 mm Insulator Material Ceramic Manufacturer Heat Range 7 Seat Type Flat Center Electrode Diameter 0.098 in Ground Electrode Material Nickel Core Center Electrode Material Nickel