This adapter allows for the installation of OEM or aftermarket air cleaners with recessed backing plate on Keihin CV carburetors. At least that’s what it is intended for, but of course, you can mount any air cleaner, carb cover or air horn with a Tillotson, Bendix or Keihin bolt pattern. It is also useful with large or low mounted gas tanks, because it positions the air cleaner further to the right by 21 mm.