The TRNR Gym Ball is a 55cm diameter exercise ball that helps improve core strength, balance, coordination, range of motion, joint stability, and postural alignment by adding instability to your workouts. It comes with a manual pump, an innovative dual tool for inflating and deflating the ball, and an exercise poster, and a free app. It is latex, BPA and phthalate-free, anti-burst, and non-slip, with a matte finish and a TRNR custom design.