I got mine as a gift, and it was fun to play with and compare scores against my brother. It was branded as a rehab tool, which maybe it could be in controlled and informed use, but I don’t think either of us considered it a workout tool as a first impression; it seemed more of “as-seen-on-tv” Fushigi/Shakeweight garage sale dollar bin fodder. To it’s credit, my brother and I were competing with each other all night going as hard as we could to beat the highest number. In that regard it was fun, but I didn’t feel like I was doing an exercise after about a cumulative hour of attempts that were done through the evening. Build wise, it’s a pretty solid feeling plastic and has an interesting tactile feel as it gyrates around the mechanism in there, but I did still feel like an oddball toy. My big gripe was that going so hard on trying to reach the highest score on like a dozen attempts did lead to my first tennis elbow spell. I didn’t realize how seriously awful that injury was to get and it took me 2-3 months of very intentional forearm extensor rehab exercises just to get my grip back strong enough to hold a 40 oz yeti water bottle or more than a bag of groceries in that hand (shout out to Great Ape Grips and Ironmind Expand-your-hand bands for getting me back in the game). I threw mine away the next day and will never use one of these again because of the injury experience coming from what I considered to be within the middle of the bell curve of expected use, but I also won’t be so closed minded to think that what led to my injury is the only application that people will find for it.