Denso Iridium Power Spark Plug #7 Heat Range SINGLEDenso Iridium Power A next generation spark plug that draws out engine evolution with a high performance spark for improved acceleration. For drivers that care about performance. By using a 0. 4mm diameter iridium alloy center electrode and a special ground electrode, IRIDIUM POWER realizes spark performance unseen until now. It steadily gives a high level of response under a variety of driving conditions. The result? Increased acceleration and torque