The over-ball comes in two sizes 21cm and 23cm in diameter. If you have a smaller frame the 21cm ball would be an appropriate size, taller and larger frames would be better suited to the 23cm ball. The ball can improve core strength, stability, mobility, flexibility and posture. You can work on your abdominal and back strength, spine mobility, rehab injuries, balance-coordination. It can also be used for release work, mobility training, proprioception and movement awareness. The ball is easily inflated with the breath a tube is included so no pump required. The ball can be deflated and inflated easily, so is convenient to carry and store or take on holiday. It is slightly textured and non-slip. Made of soft, low odour material which is flexible, durable and anti-burst. The balls are manufactured through a process that ensures no toxic emissions are released into the atmosphere so are environmental friendly. Made from eco-friendly PVC.