The fine Iridium tip ensures high durability and a consistently stable spark. Iridium alloy has extremely high melting point, perfect for today's high-tech, high-performance engines. Trivalent Metal Plating - superior anti-corrosion and anti-seizing properties. Outstanding acceleration, high fuel efficiency and durability. Ultimate design, technology and performance. 

These are one step colder plugs and are recommended for higher horsepower applications. A higher heat range number does not improve engine performance, it increases the plugs ability to dissipate heat.