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, can dissipate heat more easily, is better protected from melting, cracking, and other limitations found with standard plugs. These plugs were designed for use on tuned and higher output vehicles that benefit from a plug cooler than the factory heat range. They are great for high boost, high cylinder pressure, high cylinder temperatures, and high power situations, and they pair nicely with a set of APR ignition coils, where applicable.