This Tilta 77mm Adapter Ring allows you to mount the Tilta Mini Clamp-On Matte Box on lenses that have a 77mm front diameter. The adapter ring screws onto the front of the lens, and the matte box then clamps onto the adapter ring. The thumbscrew on the side of the matte box is used to secure the matte box firmly to the adapter ring. The adapter ring also provides a thread for attaching 77mm screw-on filters to the lens. This is done right before mounting the matte box. After attaching the adapter ring to the lens, screw on the filter to the provided thread, and then attach the matte box. The adapter ring is made of aluminum and comes in black.