This product is excellent for individuals suffering from shoulder or rotator cuff pain. I came across this product by accident after asking my former orthopedist, Dr. Wing Chang, the inventor of this product, was looking for. I fell at work and sustained a rotator cuff injury and wanted a second opinion. Little did I know that he had retired and invented a product to help with shoulder injuries. The shoulder ball acts specifically on the rotator cuff muscles of the shoulder and fixes the wrist. It's not easy, but once you learn how to move the ball without making it bounce, you'll feel those muscles working. After months of physical therapy with traditional resistance bands and push and pull exercises that didn't benefit my shoulder, I noticed an improvement in my shoulder area after a month of use. I will continue to use it and recommend it to anyone with rotator cuff or shoulder pain.