This is a good item for optimising space. If you want to have a place to put your sheet music but don't want to have another actual stand (because, let's be honest, mic stand + music stand + another instrument can be quite overwhelming in terms of space), this is a very good option.
Pros:
1. It attaches easily to a mic stand and stays there (I have not tried very heavy sheet music, but I think it would work fine).
2. It is quite small so you can also transport it easily (for example, it fits into the outside pocket of my Roland CB-61 RL with many other things inside).
Con:
The only con I find is that it might be too small for sheet music books since it is as narrow as an A4 sheet and it attaches to the mic stand. Depending on where exactly you attach it, the mic stand's arm could make it difficult to view 2 pages at the same time.
All in all, I think it is a good product if you are using smaller sheet music and you want to optimise your space.