The perfect size, shape and texture for improving your Pilates technique. Soft and flexible, it comforms to the body and provides excellent feedback for core exercises including abdominals, oblique abdominals, back extension and lateral flexion. Strong enough to kneel on, it can also be used as an unstable surface under the torso, foot, or knee. Quickly inflates (up to 12″/30cm) and deflates, to desired level of inflation.