DENSO’s commitment to technology has produced the most advanced spark plug on the market: the DENSO Iridium TT®. These spark plugs deliver the best all-around performance, exceptional fuel economy and extraordinary endurance. In fact, they’re designed to last beyond 100,000 miles, all while providing better horsepower, torque and fuel economy than any other spark plug. DENSO Iridium TT Spark Plugs – for drivers who know that true performance is more than just speed. With it’s unique design, there are literally two “tips”: a 0.4-millimeter Iridium center electrode, and a 0.7-millimeter Platinum ground electrode. DENSO’s patented Twin-Tip technology was first used on original equipment spark plugs for luxury and performance cars. Now, that technology is available to everyone.