Light & Motion - Arm Base Spring lock
Light & Motions patented spring lock system.
Can be mounted directly on a base mount.
The base mount is a standard item on any LMI housing handles, but can also be bought separately and mounted on anything.
(other housings or tray systems)
It ends in a 3/4" locline mount.
You can get the 3/4" -> 1/2" adaptor and use 1/2" items.