NGK BPR7HIX Iridium Spark Plug NGK BPR7HIX Iridium Performance spark plug for various makes and models. Thread Size: 14mm Reach: 12.7mm (1/2 inch) Hex Size: 20.6mm (13/16 inch) Electrode Diameter: 0.6mm Gap: 0.8mm (.031 inch) Heat Range: 7