I have one and it's nothing special or expensive, it just fits me really well which I think is the key factor really. Will try to remember to check and see what make it is tomorrow when I go to yard.
It's more of a lumbar support type thing but does the job really well for my lower back issues.
I have a back on track one. I cringed buying it due to the cost and worry it wouldnt work. It really, really does work compared to a "normal one" and was worth every penny