BPR6FS Spark Plug | NGK 2623 Premium NGK spark plugs are known for their reliable performance and superior anti-fouling characteristics. NGK spark plug BPR6FS Stock number 2623 14mm x 1.25mm thread Projecting insulator type Resistor Tapered seat Standard type Gap 0.031 in. (0.8mm) 5/8 in. or 16mm hex Replaces Mercury 33-97389