The Zacuto Tri-Mount Rod Adapter mounts a 15mm rod of a camera rig and adapts two rod-mounted accessories, such as a mic and viewfinder, onto the rig. Tri-Mount is T-shaped and features a rod opening on top and two on the side. The top one is for mounting and the other two for adapting. The top one tightens by Allen screw, the other two by levers for quick-release use.
Tri-Mount's most common use is to attach a Sony FS100 mic to a Zacuto FS100 Top Handle and to additionally attach a viewfinder, a light, an articulating arm, or a recorder. But you can do pretty-much anything you can think of with three 15mm rods...(the top opening has a bottom, the side ones go through from end to end).