The 20mm and 35mm Canon FD Macrophoto lenses can be checked out on this site. They are designed to be used with a bellows unit and I have found the need a lot of light for focusing.

Combined with the Canon FD-EOS Macro Lens Mount Converter they can be used with the Canon EOS line of cameras.

They open up a whole new world of macrophotography compared to the normal macro lenses.