l bought it since it looked more practital than the usual foot shaker that is strapet on your shoe. This one you just need to slip in you shoe, takes only a second.
It takes time though to find the perfect position, be it on the sides of your shoe or directly behind your heel as picture suggests. Also I found it to be a great hand shaker, and due to its handle, you can get greater control and expression as opposed to regual shaker egg. Only con: It could be cheaper.