NGK R0451B-8 (9356) - Racing Spark Plug / Sparkplug. This spark plug is designed for racing applications. Key specifications include: Thread Length: 26.5mm, Outer thread: 10mm, Hex Nut Size: 14 mm, Spark projection: 0.5mm, Connector Type: Fixed SAE. It features an Iridium centre electrode and a single earthed electrode. Type: interference Suppression 5 kOhm. Gasket Type Seat. Quantity: 1 Unit. As the main source of power in any petrol engine, a spark plug performs an essential function: It is responsible for igniting the air-fuel mixture in the combustion chamber of petrol engines. This combustion process creates power, ultimately setting the vehicle in motion. NGK Spark Plugs are high quality and have a unique design to guarantee the best possible performance with a wide range of different heat ratings.