aFe Power Silver Bullet 46-33004 Ford Throttle Body Spacer Precision machined from 6061-T6 billet aluminum Serrated/Helix Combination Design for optimum airflow into the combustion chamber Eliminates annoying whistle found in helix only throttle body spacers Includes all hardware This product is 50-state legal (CARB E.O Number D-550-11)