NGK Racing Spark Plugs have been designed to withstand the rigours of racing applications. Tuned, racing-engines are often subjected to speeds in excess of 15,000rpm during races which means that temperature, pressure, vibrations and currents in the conbustion chamber are so extreme that conventional earth electrodes could break or melt. NGK Racing Spark Plugs are designed with a ring-shaped earth electrode which means that the spark creeps from the middle electrode to the earth electrode instead of jumping.