Denso iridium spark plug helps your vehicle achieve unparalleled performance. This is achieved by a combination of an ultra-fine 0.4mm diameter iridium center electrode with a tapered cut u-groove ground electrode. Iridium conducts electricity better than platinum, however what makes it exceptional is it is also 6x harder and 8x stronger than platinum. Because of this, the center electrode can be machined down to 0.4 mm. This ultra-fine iridium center electrode provides superior ignition performance during acceleration and top cruising rpm. The u-groove ground electrode creates a larger, brighter flame kernel. The tip of the ground electrode has been tapered which further improves firing performance by reducing quenching. All of these features combine to give more horsepower to your motor.