Excellent. Personally, it worked for me. It doesn't open my jaw. I must, however, emphasize that depending on the adjustment to the millimeter, as they say, it may cause prolonged pressure on the jaw inward all night. I don't know if it can cause a long-term jaw position issue if not used carefully. With experimentation, I believe you can find what suits you.

I got it because I wear a mouthguard while sleeping due to snoring for jaw support. In the end, it doesn't work because it's clearly only for a CPAP mask during which you have to sleep only on your back; otherwise, in any other sleeping position, it comes out and moves from its place. Generally, I would say it easily comes out of its place anyway. Very simple construction, its price should be a maximum of 10 euros. In my opinion, it's not worth it; I regret buying it for what I wanted.