NGK's IX Iridium Series Plugs were Designed Specifically for the Performance Enthusiast. Fine Wire Center Electrode Ensures High Durability and a Consistently Stable Spark Iridium Alloy has an Extremely High Melting Point, Perfect for Today's High-Tech, High Performance Engines Trivalent Metal Plating Provides Superior Anti-Corrosion and Anti-Seizing Properties Corrugated Ribs Prevent Flashover Pure Alumina Silicate Ceramic Insulator, Provides Superior Strength and Better Heat Transfer Copper Core Aids in Heat Removal Triple Seals Prevent Leakage