This Genus Adapter Ring for Select Clip-On Matte Boxes threads into lenses with 82mm threaded front, providing a 93mm diameter clamping surface for your Genus Matte Box Lite or Genus Wide Matte Box. Please note that this is not a filter-retaining ring. It is designed to mate your lens with a Genus Matte Box Lite or Genus Wide Clip-On Matte Box. It is made from anodized aluminum for strength and durability, and recommended for use with a lens that does not have a rotating front.