NGK IRIDIUM IX Spark Plugs, 14mm Thread Size, 11mm (7/16″) Reach, Fine Wire (0.6mm) Gap, Heat Range 5 to 60°C. The plugs are sold in packs of 4 and come with a lifetime warranty. The spark plugs have a life expectancy of five years. They can be used on any vehicle or motorcycle. Notably, the new plugs were launched by Indian manufacturer NGK in 2015. The plugs are available in four different colours.