The ultimate in the evolution of spark plug technology and performance from the industry leaderThe iridium electrode is 25% smaller than a platinum electrode, and it's just 1/4 the size of a conventional nickel electrodeUltra-small-diameter center electrode reduces voltage requirement and extends ignition system lifeNew metal shell plating has enhanced anticorrosion qualities NGK Single 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 Longest Life Available