For stronger back musculature, use Securemax Exercise Balls by SISSEL®. This exercise ball can be used as a chair at home, at work or even in school. It is not only used by physical therapists for training but also ideal for ordinary people who wants to correct their posture. The ball's surface is latex and phthalate free making it safe to use. It can also resist up to 130kg and will not burst once punctured, instead, it will gradually release air. It comes in various colors to choose from such as blue-purple, red, silver or grey. It has also different sizes such as 45cm, 55cm, 65cm and 75cm depending on the needs of the user.