NGK reference : R2558E-9
NGK Racing spark plugs are designed for race or high tuned engine. They use precious metal as Iridium, Platinum or Gold-Palladium. Their high thermal index (cold spark plugs) allow a better heat transfer. The spark plugs are designed to handle very high temperatures, high pressure and vibrations, things that standard spark plug can't handle with reliability. Thats why the NGK Racing range fit a ground electrode with a flat ring shape.
