This aluminum backing plate has an integrated velocity stack, providing a better airflow for increased horsepower and torque through the entire RPM range. Kit comes complete with, low restriction air cleaner element, gasket, and all required mounting hardware. Fits all Keihin CV carburetor equipped Evolution Big Twin, Evolution Sportster, and Twin Cam, as well as all Delphi Fuel Injection equipped Twin Cam models with cable operated throttle. Must be used with OEM round or oval air cleaner cover and air cleaner support bracket.