Denso Spark Plug Iridium plugs have an extremely long life as Iridium is 6x harder and 8x stronger than platinum. Because of the strength and hardness of iridium, there is virtually no electrode wear. This combined with a platinum ground electrode, creates a spark plug that is almost impervious to wear even under extreme driving or racing conditions. Technical Specifications - Extra Long Life Iridium Plug, 14mm Thread, 19mm (3/4") Reach, 5/8" (16mm) Hex Size, Gasket Seat, Resistor, Solid Terminal, 0.7mm Fine Wire Iridium-Tipped Center Electrode, Platinum Tipped Ground Electrode, .044" (1.1mm) Gap