NGK R7420-10 / R742010 / 5501 Racing Spark Plug Replaces IRE01-31 To withstand the severe conditions that occur in racing engines, NGK Racing Spark Plugs feature electrode materials and configurations as follows: 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.BOX DIMENSIONSHeight (mm): 95Width (mm): 24Length (mm): 22 If you are unsure as to whether this is the correct part for your vehicle, please don\'t hesitate to contact us. Alternatively please use the cross reference table above.