An inflatable (comes with inflation device), air-filled sponge ball with a unique soft-stretchy "skin" to massage and activate your core and stretch your psoas. This special, soft massage ball allows you to gently and safely access your innermost abdominals. (approx. 22" round circumference and 7" high but can vary up to 1"). The coregeous approach allows for an intuitive play into self massage that can liberate and unlock key tension zones that will help you breath better and live more lightly in your body.