Bosch (7538) WR11E0 Super Spark Plug, (Pack of 1) Heavy Duty Yttrium-Enhanced Center Electrode with Copper Core Provides Superior Reliability and Durability Tapered Cut Nickel Chromium Ground Electrode Assists in Cold Weather Starts and Provides Increased Ignitability,Nickel-Plated Rolled Threads Provide Anti-Seize and Corrosion Protection Metal Glass Fused Resistor Gives Maximum Interference Suppression,Angular, 5-Rib Insulator Design Prevents Flashover Center Electrode: Material: Nickel, Type: Standard, Size: 2.5mm. Shell: Thread Size: 14mm, Thread Pitch: 1.25mm, Seat Type: Gasket, Resistor: Yes, Reach: 9.5mm (3/8"), Hex Size: 13/16" (21mm), Terminal Type: Removable Nut, Gap: .031" (0.8mm)