Oh, it is very useful! The unique design of combining four 15mm rod clamps helps to raise an extra 30mm height from the bottom. It comes with wingnuts to lock 15mm rod tight. It features quick releasement and attachment.
I just purchased this about 2 weeks ago. During my first gig with it, the rods (SmallRig Carbon Fiber) came loose from the clamp resulting in my camera hitting the ground. I then tried to tighten the arms more so it would be solid, but I ended up stripping the screw on one side, so now it's basically useless once I have to remove it from my rig.
Aside from that, it does exactly what it's intended for - adjusting the height.