NGK (4492) R6918B-8 Racing Spark Plug, Pack of 1 Fine-wire center and ground electrodes provide better sparking and enhanced ignitability Made to withstand the severe conditions that occur in racing engines Zinc dipped shell prevents corrosion while the triple gasket seal eliminates combustion gas leakage Special configurations are used for the insulator noses to improve throttle response and prevent fouling with corrugated ribs on insulator to prevent flashover Many use precious metals such as platinum or gold/palladium for greater durability and lower voltage requirements