Useless.
I received one of these things almost a week ago after ordering it here on Amazon, and after trying to use it every day for this period of time, I can safely say that the cheapo trays you boil and mold, which I despise by the way, are leagues better than this piece of junk. Even when I followed the included directions, I could not get it to fit to my teeth well at all. It could get something of a vaguely decent fit with a lot of effort(straying from the included directions stating to "try to swallow repeatedly" in the process), but in doing so, the whitening gel would get smeared onto my gums(ouch). It did technically prevent drooling by blocking the saliva from leaving my mouth, but then the saliva would just accumulate to the point where it would fill my mouth up and I'd struggle to avoid swallowing it. I'm going to order more of the cheapo boiling trays and throw this thing away.
Rating: 1 stars