I'm going to keep it short and to the point.
It does reduce the sound to a level comfortable for the ones around you. However, don't expect to be muted by the definition of the word. It does the job as long as you have realistic expectations. The mic is surprisingly good and it gives you the opportunity to hear yourself properly and not out of tune as I'm gonna mention below.
Built quality, decent as long as you treat it as you treat your saxophone (assuming you take care of your sax).
Now, expect to lose your comfort of playing freely as your hands are cramped inside the small holes and you can't reach the palm keys easily in both hands. I guess you can get used to it though. Or not.
Lastly the biggest negative is that without headphones you sound out of tune and unfortunately forget any decent sound below the low C. Long notes below C (even if you manage to make them) the sound makes a weird wavy circulation. However, I find it interesting that staccato notes with a little luck and practice can be heard. Again, expect no tune and quality of the low notes below C.
Overall, if you live in an apartment and you don't have a spare room to make it your studio, or you don't have a basement or any other option. That mute does the job.
