When you re passionate about performance you need a technologically advanced plug. Autolite Iridium XP utilizes an iridium-enhanced 0.6 mm finewire and proprietary platinum sidewire for improved durability and a more focused ignition for better overall ignitability providing optimum performance. Now with a lifetime limited warranty! Thread Size 14mm X 1.25. Reach: 0.708 Hex Size: 5/8 (16mm) Seat Type: Tapered. Tip Configuration: Long Projection. Metal Type: Iridium. Terminal Type: Solid. Set of 8.