I had a similar clamp in my kit which came with a previous pencil instrument microphone. I couldn't remember what it was called but after a bit of searching this came up. I did the sound for a house concert recently with lots of people coming and going on stage. I had on of these clamps half way up each microphone stand with a butterfly wing quick release microphone holder on each. Using AKG C1000 instrument mics (which are brilliant but best with phantom power) I got a really good sound from guitars, accordion, banjo etc and it's easy to point the mic where you need it. I even got a great sound from an electric piano! If you are pushed for time with regard to sound checking or don't want to rely on the variable quality of pick ups on instrument then using these clamps with decent mics is a nice way to do it. Great quality and value!
I use this to mount a Studiomaster mic stand monitor on a Hercules mic stand. The mounting kit that comes with the monitor sits it too high and is therefore prone to feedback. By using this clamp lower down the stand it avoids feedback and the lower centre of gravity makes the whole thing much more stable. The clamp seems well made and strong enough to hold the monitor securely.
This is one of the best, excellent when attaching to boom and anytype type pole, be sure to buy a mic holder adaptors if you need it, as it is a 3/8 size