Great for ankle strength!! I was a gymnast and this helped me so much with balance. It's also a great activity if you sprain ankles easily. Very effective product, worth the price. It's lasted many years so far with heavy use
I tried to sit on one of these while doing computer work to strengthen my core. I have scoliosis though so it made my back so much more sore. My doctor said he doesn't recommend these to patients with scoliosis because it puts pressure on the wrong spots.