This set of 8 Champion Spark Plugs, model number RBL15Y4, is a great addition to any vintage car or truck with a gasoline engine and a 12V voltage system. These copper plugs have a standard configuration and a 14mm thread diameter with a 16mm hex size. The installation depth is 11.2mm, and they replace the following part numbers: 2139, ASF42CF4, and RBL15Y4. These spark plugs are made in the United States and are in new old stock condition. They are compatible with various ignition systems and components and are ideal for anyone looking to replace their old or worn-out spark plugs. With Champion's reputation for quality and reliability, you can trust that these spark plugs will improve your engine's performance.