The Pilates Mini Ball is a great way to engage your abs and inner thighs while increasing your flexibility, strength and endurance! It is also aids in providing support for abdominal muscle training and neck massages. It can also be used as a cushion, when it is partially inflated. The Pilates Mini Ball is easy to inflate by gently blowing into the inflation straw (included). The ball is 20 cm (7.87") in diameter.