Have heard, and read the web page, but wonder about the effects. Said to provide safe traction on the neck vertebrae, muscles, etc. It's a foldable lightweight bendy plastic form placed on the floor (mat) and you lie on it. The bendy part provides some tension between your shoulders and skull to pull the joints apart, a tiny bit.

The website is kinda crappy, IMO, but here it is:

https://www.necksaviour.com/