The ACCU-Beam® Dual Adaptor provides simultaneous video and digital photographic documentation. . Adaptable to Surgical Microscopes from Zeiss, Leica, Moller-Wedel, Global, Seiler,Aus Jena, Kaps, Topcon, Vasconcellos, Marco, Takagi and Inami. The adaptor has 28mm threads which screw directly into digital cameras with 28mm filter threads. Cameras with larger filter threads require an intermediate step up ring.U.S. Patent No. 5,264,928