If you installed a new 21100-61012 desmogged carburetor to a '75 to '80 Land Cruiser FJ40, this aluminum spacer will enable you to close the gap between the top of the carb and the stock air cleaner assembly.
Background: The original carburetor for these years contained a spacer sandwiched in the mid section for the EGR circuit, thus it was taller than the desmogged carburetor without the EGR layer. Adding this spacer will line up the top of the new carburetor to the air cleaner.