NGK 5238 Racing Spark Plugs R5671A-9 From professional racers with extremely modified engines to the weekend warrior, all levels of performance enthusiasts’ count on the advanced technology built into NGK Racing Spark Plugs. To withstand the severe conditions that occur in racing engines, these spark plugs are designed for use in engines that have been tuned to achieve maximum power under specific racing conditions. Features: Electrode materials - Many use precious metals such as platinum or gold/palladium for greater durability and lower voltage requirements. Electrode configurations - Fine-wire center electrodes provide better sparking and enhanced ignitability. Fine-wire ground electrodes further improve the ignitability of the plug. Insulator configurations - Special configurations are used for the insulator noses to improve throttle response. Stock Number: 5238 Center Electrode Core Material: Copper Core Center Electrode Tip Material: Nickel with V Groove Gap Size: 0.032 in. Ground Configuration: Standard Ground Electrode Core Material: Nickel Core Ground Electrode Quantity: 1 Ground Electrode Tip Design: Standard Hex Size: 5/8” Manufacturer Heat Range: 9 Resistance: Zero ohms Seat Type: Gasket Thread Diameter: 0.551 in.