The device works well on parts of the back, ...
The device works well on parts of the back,  but roughly on the neck. The company that advertised and shipped it might be questionable. The very short users' manual has two big faults that do not inspire confidence. First, the manual in English is badly composed, has bas mis-spellings, and full of incomprehensible word usages and sentence structures. Second, neither the manual nor the packaging provides the name of the manufacturer or seller, contact information, nor any suggestion of warrantee or repair policies.
Rating: 1 stars