Iridium TT Spark Plugs utilize decades of Denso experience developing the some of the best spark plugs available on the market today. Combining all the best features from the entire Denso family of spark plugs, the Iridium TT offers you more power in a more versatile plug. Engineered with the smallest tip on the market, giving you unmatched fuel economy over any other plug. Endurance and reliability is also unparalleled, lasting beyond 100,000 miles for today's most popular makes and models.