We've taken one of our best-selling 37" therapy balls, filled it with 1400 grams (3 pounds) of sand. The overall benefits is that it won't roll away when you finish using it. The Stay N Place Ball is great for traditional balance therapy, as a chair, or for encouraging proprioceptive responses when lifted or passed around. It has the same great feel as an ordinary therapy ball with the added benefit of weight. Color may vary. Latex free.