Professional Products 20001 AIRFLO Insert Cleaner The AIRFLO is an amazingly simple device that will work on Holley or Demon four barrel carbs, with or without a choke tower and any round air cleaner with an inside space of 3.3" to 6.4" The AIRFLO works on a very simple principle As air flows into the air cleaner, the air currents collide in the center and are slowed making their entry into the carburetor The AIRFLO solves this problem by providing a smooth transition from the side entry right down into the carb Tests have shown anywhere from 7 to 10 HP and as much as a tenth better etc.