Dinan Iridium Spark Plugs are an excellent upgrade for tuned, and even stock engines, where applicable.* Our spark plugs are made from Iridium - one of the strongest materials available. They last longer than other materials with higher melting points, run cooler, resist preignition, and even require less voltage to produce a strong spark. The iridium electrode with its copper core is harder and stronger than other materials, can dissipate heat more easily, and is better protected from melting, cracking, and other limitations found with standard plugs.