NGK Iridium Spark Plug for Yamaha R15 V1 /R15 V2 , CBR 150R/125RNGK Iridium Spark Plug for Yamaha R15 V1 R15 V2 , CBR 150R 125R NGK Iridium spark plugs use very precious Iridium metal at the tip of center electrode of diameter 0. 6mm and has a thermo edge design for central electrode. These features give anti carbon fouling performance, smoothest running, and excellent acceleration with increased mileage and are used and appreciated by most racing bikes and cars all over the world. NGK Iridium Spark Plug : Part