NGK 4554 (R5671A-8) Racing Spark Plug, Pack Of 4 Special Insulator Nose Configurations Improve Throttle Response Corrugated Ribs Prevent Flashover; Copper Core Aids In Heat Removal; Triple Seals Prevent Leakage Pure Alumina Silicate Ceramic Insulator; Provides Superior Strength And Better Heat Transfer Specs: Thread Size - 14mm; Pitch - 1.25mm; Seat Type - Gasket; Terminal Type - Solid; Gap - .031" (0.8mm)