Turbulator fits 4 bolt 1 3/4 inch SU upsweep and straight manifolds. The Turbulator lineup from M&T Engineering will literally turn your intake manifold into a violent mixing chamber. The heavier fuel particles are directed away from the sides of your intake manifold back to the center of air flow. The fixed vane Turbulator then tumbles the mixture resulting in higher horsepower and a faster, more responsive machine. For street or drag strip use, no matter what fuel/carburetor combination, the Turbulator is guaranteed to increase the performance of your H-D.