The Fitness Mad 300Kg Anti Burst swiss ball 55cm is designed to help you improve balance, muscle tone and flexibility, as well as to strengthen the core muscles. This lightweight and durable ball is suitable for Fit Ball workouts, yoga, Pilates and physiotherapy and can be used as a chair to aid with postural problems. The ball is rated as suitable for 300kg (661.4lbs) load and has been SGS Labs tested as burst-resistant at over 500kg (1102.3lbs) static load. It is 55cm (21.7”) in diameter which makes it suitable for people who are 5'6” (167.6cm) in height and under.