Sometimes we want to mix and match parts different than Henry planned. These spacers allow you to swap distributors around on your flathead. This adaptor fits most aftermarket performance cams. In some cases, earlier stock engines may have a "shallow-nose" camshaft. If that is the case, the drive tang on the distributor will not contact the slot in the cam and the distributor will spin freely after installation. Should this occur, you will need to purchase a cam button spacer such as Speedway # 910-12710.