The 80mm Clamp-On Adapter for MB-T12 Matte Box from Tilta is used to attach the matte box to a lens with a 80mm front diameter. The adapter attaches to the lightweight 4 x 5.65" matte box via keyhole slots and fastens to the lens using a screw-on clamp.
This aluminum and stainless steel adapter has a rectangular outer shape and a circular inner design.