Denso (3139) K20R-U11 Spark Plugs, Pack of 4 CHOOSE CONSISTENT COMBUSTION: the DENSO Standard U-Groove Spark Plug employs a unique, channeled ground electrode designed to generate a larger spark nucleus at the point of ignition. Greater spark energy means improved flame travel, producing more complete, consistent, and efficient combustion GAIN GREATER FUEL EFFICIENCY: the u-groove ground electrode was developed to improve ignitability for increased efficiency in emission gas purification and fuel consumption IMPROVE THROTTLE RESPONSE: this spark plug fires leaner mixtures than conventional plugs and improves throttle response ENSURE RELIABILITY: the DENSO Standard U-Groove Spark Plug is 100 percent pre-fired to ensure reliable operation and lasts twice as long as conventional plugs ENJOY TROUBLE-FREE PERFORMANCE: the unique five-rib insulator reduces flashover and decreases voltage loss while the dual copper and glass seal combines the center electrode and insulator together for a gas-tight seal