NGK: Racing plug
10mm, 3/4" reach, 5/8" hex, gasket seat, resistor, surface gap, removable terminal nut, 1.1mm gap
Racing surface discharge plugs may be necessary in high compression applications or when valve/piston clearance does not allow for a ground strap and a retracted tip plug is not appropriate due to insulator/tip exposure. While they are nearly immune to preignition, they can be susceptible to fouling when used in colder applications. NGK surface gap plugs are hand made in Japan and constructed to withstand the most extreme racing environments.