The Zacuto Z-QML lightweight Q-Mount is a universal mount for 15mm lightweight rod systems. It attaches underneath the rods without removing any equipment.
This device is used to mount Zamerican arms, to create a lens support and is used to mount various other devices utilizing Zacuto Zuds.
The bad news about Zacuto stuff is it's expensive. The good news is it's so well designed and built, it's actually worth it. This Q-Mount is the perfect solution to mounting a monitor on an arm so that you don't have to worry about it falling over or coming loose during a shoot. I use it with the big Zamerican arm, and it's a killer combo. I started out with the smaller z-mount, but found it slipped occasionally. So to avoid having to over crank it to get it to hold, I upgraded to the Q-Mount. Problem solved forever.
It's made by Zacuto. It's pricey, but it's the best quality you will find. I use this in tandem with a variety of Zacuto lens supports for larger (300-400mm) lenses. After hundreds of uses, the Q-Mount still performs as if it's new. Great product.