I like that they use a spring unit as a foundation since that is key for proper spinal alignment. (mommypotamus.com)
They allow the body to stay in motion (some more than others), and also help the pelvis maintain a proper tilt for good spinal alignment. (wellnessmama.com)
Now you can improve your balance and posture, as well as strengthen your core muscles and improve spinal alignment all while sitting at your computer! (thefashionablehousewife.com)