So I bought this item mainly because of the price, and the fact that it had great reviews.
I ordered 3 systems for me and my band mates to use for our guitars, only to realize that the system has a fixed frequency that is unchangeable. That to me is ridiculous. This automatically meant that I can't use it with my band mates, as soon as a second unit would power up there would be horrible interference.
We decided we'll keep one anyway for our bassist to use. The problem was whenever he struck a note there would be an accompanying hiss with it. Every time he'd play something, there would be horrible hiss. So, naturally we ditched that one too and we're sending all of them back to Thomann.
Also, the build quality is poor and honestly wouldn't trust using something like this in a professional situation.
Conclusion: if you need something professional, just invest more and buy a decent wireless system.