Good tool for working muscles. Came with no instructions though they do offer them online a their website. Wife has been using it and though she states it’s hard, it does help with her lower aback pain shh just Ds tooth herself to use it. I won’t offer any medical claims beyond that as I am not a doctor and no clinical study done.

There aren't any instructions included, so I'm not sure I'm doing it right. I placed it on the floor and layed on it where I thought it would feel good, and it did but also it felt kinda weird, so I moved it, but still not sure I had it in the right location. I wish it came with an instruction sheet or even better, a video were included on their website.