APR Iridium Pro Spark Plugs are the excellent upgrade for tuned engines. Our spark plugs are made from Iridium, which is one of the strongest materials you can use in this type of application. They run cooler, resist preignition, last longer than other materials with higher melting points, and even require less voltage to produce a strong spark. The electrode is harder and stronger than other materials and with its copper core can dissipate heat more easily.