I'm using these for mics, cameras, mic booms, stereo bars and whatnot, and it's an absolutely brilliant way of quickly moving things around between different types and sizes of stands! (I have very limited space, and prefer to not have more gear than I really need.) Robust construction, and very easy to use.
However, there is a fair bit of rotational play, which is not very helpful if you want things to lock into an exact direction. I'm using two of them on the actual stereo mic bar, so I can easily detach the mics and use them separately, but the precision leaves a bit to be desired in this case.