Bosch (4309) HGR9LDP0 9 Platinum + 2 Spark Plug, (Pack of 1) Revolutionary surface air gap firing technology featuring two yttrium-enhanced ground electrodes delivers a longer, more powerful spark for optimum engine performance Two yttrium-enhanced ground electrodes provide optimum access to the air/fuel mixture for more efficient combustion...plus a longer performance life More platinum in the center electrode further increases performance life Electrode gap is factory set to provide ease of installation never requires adjustment Provides ease of installation -- never requires adjustment