Engine Carburetor Throttle Shaft Conversion Kit Slabbed Throttle Staft For 4150/4160/4150HP Carbs ProformUpgrade your PROFORM or Holley carburetors, up to 1 3 4 inch throttle bores, to achieve higher air flow by reducing the size of the throttle shaft. Each kit includes button head Torx throttle plate screws, universal lever, and slip link secondary activation system. The High Flow kit includes stainless steel button head screws. Sold as one kit. Product Details: Engine Carburetor High Flow Throttle Shaft Conversion Kit For 4150 4160 4150HP Carburetors