Stronger than platinumVirtually no electrode wearExtra long-life plugIridium plug, 14 millimeter thread size, 26.5 millimeter (1.04 inch) reach, 5/8 inch (16 millimeter) Hex size, gasket seat, resistor, extended reach, solid terminal nut, 0.7 millimeter iridium center electrode, .044 inch (1.1 millimeter) gap, heat range: 20.