Probably something for well-trained people

The device may be suitable for people who are already well-trained and possess sufficient force to bring the relatively short rod to vibrate and keep it in vibration. For all others, he seems to me to be less suitable. Although the shortness of the rod may be convenient, but in this way it oscillates at a much too high for my liking frequency. In my opinion, the device is not a substitute for the Flexi-Bar.