The tethermate for imac is a portable aluminum plate witha stability bar that offers a simple and portable solution for shooting direct to your laptop on location. The 22” x 15.7” (560 mm x 400 mm) size includes 1/4"-20 and 3/8"-16 female threads on its underside to mount directly on tripod or any equipment that comes with 1/4"-20 and 3/8"-16 male threads. Three mounting slots under the portable plate make it easy to connect additional accessories withthe u-shaped sliding plate. The spring located knob is also included to keep the u-shaped sliding plated in place.