This set of spark plugs from Splitfire is perfect for small engines that require a reliable and high-performance ignition system. With a thread diameter of 14mm and a voltage of 12V, these spark plugs are compatible with a wide range of engines. The copper material ensures efficient heat transfer and a longer lifespan. These spark plugs are interchangeable with part numbers 456, 845, XST458, and W14LM-U, making them a versatile option for various vehicles. They are manufactured in the United States and are not vintage parts. Improve the performance of your engine with these Splitfire SF45F spark plugs.