Stretch and strengthen muscles in the comfort of your own home, gym or classroom with this 17-1/2" Exercise and Therapy Ball. It is constructed of a thick, sturdy material that provides a stable surface for your workout routines. This heavy-duty exercise ball is designed for limited movement forward, backward and rotating. It is ideal for balance therapy activities with special education purposes. With many uses, this versatile ball is the smart choice for those needing to improve physically.