We offer both 73mm, 76mm, and 80mm units by themselves, and they both deliver a noticeable improvement in performance on both stock and modified 5.0 Mustang vehicles. The factory 55mm unit on these vehicles flows 550 cfm and is actually 5mm smaller than the stock throttle body. The 73mm unit flows 700 cfm and the 76mm flows nearly 800 cfm, and they are both direct fit replacements for the factory 55mm unit.