NGK Iridium IX spark plugs are designed specifically for the performance enthusiast. Iridium IX spark plugs offer extreme ignitibility, improved throttle response and superior anti-fouling. The fine-wire iridium center electrode ensures high durability and a consistently stable spark. A special taper-cut ground electrode shape allows more area for faster flame expansion. Iridium alloy has an extremely high melting point, perfect for today's high-performance engines. Trivalent metal plating provides superior anti-corrosion and anti-seizing properties.