Brisk Racing B08ZS replaces 296000421 NGK KR9E-G, 296000407 NGK KR9C-G. Brisk Multi-Spark Spark Plugs are designed to deliver 3 simultaneous sparks without any modifications to your ignition system. This unique patented design is beneficial for high performance and racing applications, and everyone who is seeking more full and complete combustion cycle as there is no shrouding of the sparks. By having the Multiple Sparks unshrouded, the multi-spark spark plugs have direct access to the fuel / air mixture which produces a more spontaneous and rapid flame propagation. This improves engine efficiency as there are less imperfectly ignited cycles (reduction in emissions from unburnt fuels/air) which is beneficial for racing and performance as well as a producing an economically friendly product. See our video demonstration for a real life view of how this product works.