IU22 Iridium Spark PlugIridium Spark PlugSix times harder than platinum, iridium withstands temperatures up to 4,000F Because the iridium electrodes of these plugs can be shrunk to only 0. 4mm, voltage requirements decrease while firing performance improves 360 laser welding of electrode provides a seal that resists wear even in the worst conditions Ground electrode features a tapered cut and U groove that form a large volume area for the flame's center