Canon Control Ring Mount Adapter EF-EOS R for Canon EOS R Full Frame Mirrorless Camera. Control Ring Mount Adapter EF-EOS R offers the same lens mount conversion as Mount Adapter EF-EOS R, but also adds a Lens Control Ring.
The Control Ring Mount Adapter EF-EOS R features a Lens Control Ring, which can be used to adjust aperture, shutter speed, ISO or exposure compensation while your EOS R camera is still at your eye.