These adaptor plates bolt-on to an existing head or manifold which was originally intended for an Amal carburetor. The Mikuni rubber flange then bolts to this plate, allowing Mikuni or Amal MkII spigot-mount carburetors to be used. The small plate adapts a 2" stud spacing for 26-34mm carbs; the large plate adapts 65mm spacing to 36-38mm carbs.