Professional Products offers this style throttle body in two sizes; 80mm and 85mm. The 80mm version is typically suitable for use on stock intakes. The 85mm size is for use on the Professional Products #52060/#52061 LS1 Typhoon Intake Manifold or other LS1 aftermarket intakes. These throttle bodies feature die cast aluminum construction and are O.E. quality units. Both models include an aluminum transition plate that bolts between the stock manifold and the throttle body. This transition plate smooths the flow of air when using the throttle body on a manifold that has an inlet opening smaller than the throttle body. These units are a direct bolt-in replacement for the stock throttle body.