Denso Spark Plug Denso's standard plugs provides a Copper core for better thermal conductivity. Machine rolled threads to reduce cross-threading and seizing . The plug insulator is constructed of purified alumina powder for extreme stress with 5 ribs to prevent flashover. Product Features:Machine Rolled Threads Prevent Seizing or Cross Threading During Installation and Removal100% Pre-Fired to Assure the Highest Quality PossiblePurified Alumina Powder Insulator Provides Exceptional Strength and Thermal ConductivityFive Rib Insulator Prevents FlashoverCopper-Glass Seal Bonds Center Electrode and Insulator for a Gas-Tight Seal
