NGK (6544) IMR9D-9H Laser Iridium Spark Plug, Pack of 1 Laser welded Iridium center electrode tip ensures high durability and greater spark Platinum disc welded to backside of ground electrode provides long life Longer insulator nose prevents fouling, the corrugated ribs on insulator prevents flashover, and a triple gasket seal eliminates combustion gas leakage Faster starts and quicker acceleration Better fuel economy and lower emissions, trivalent metal plating for superior anti-corrosion and anti-seizing