Dinan Iridium Spark Plugs are an excellent upgrade for tuned, and even stock engines. 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. Dinan spark plugs are great for high boost, high cylinder pressure, high cylinder temperatures, and high-power situations, and they pair nicely with a set of Dinan ignition coils, where applicable. However, they are not only for tuned and higher output vehicles that may benefit from a plug cooler than the factory heat range – they also are applicable to non-tuned / stock vehicles as well! The D640-0001 spark plug applies to the following engines: Gen 1 B48, Gen 1 & 2 B58 engines as well as the S58. Compatible OEM Part #Cross Reference: 12120040551, 12122455258, 12120046646 & 12125A4EF60