Might want to beware of that. These bring the jaw forward, to my understanding, and believe me that is not good for TMJD.
This is not exactly a new concept. I had one 15 years ago, but when my jaw started to hurt about 3 weeks in, the dentist suspected TMJD and said to stop using it.
No refund on the rather high price though...
You are right about that because it forces the jaw muscles and ligaments into a position which strains them held in a forward position for an extended amount of time. The primary goal is to bring the tongue forward to open the airway. A better device is called an AVEO appliance. Advances the tongue without straining muscles and joints. I use one. It is very effective.
Interesting, because I saw a TMJ specialist — one of only five in the SF Bay Area. She thought it might be useful.