NGK Iridium IX Spark Plug - BPR5EIX (6597) Specifications: Reach: 19 mm (3/4") Terminal Type: M4 Thread Diameter: 14 mm Seal Type: Gasket Seat Electrode Material: Iridium Projection Type: Projected Pack Size: 1 Single Unit Resistor: Yes Tip Configuration: Single Electrode Hex Spanner Size: 20.8 mm (13/16") Part Number: 37-BPR5EIX (phoenixmotos.com) Details: NGK 6597 BPR5EIX Single Iridium Spark Plug: Designed specifically for performance enthusiasts. Fine Wire Center Electrode: Ensures high durability and consistently stable spark. Iridium Alloy: Extremely high melting point, ideal for high-tech, high-performance engines. Features: Trivalent Metal Plating: Provides superior anti-corrosion and anti-seizing properties. Corrugated Ribs: Prevent flashover. Pure Alumina Silicate Ceramic Insulator: Provides superior strength and better heat transfer. Copper Core: Aids in heat removal. Triple Seals: Prevent leakage.