Weighted stability ball! Lift it shift it shake itntogether the ball and the weighted material create dynamic resistance and audible feedback. With 21/2 lbs. of unstable weight inside it this stability ball wont roll away when youre exercising. You can perform traditional stability ball exercises plus design new exercise sequences. Its a total-body training tool thats more versatile than a traditional stability ball. Customize the size by inflating to 55cm or 65cm. 6 unique designs on the balls surface provide points of reference for exercise techniques and cueing. You can even use it like a medicine ball. Color: Translucent blue.