The training ball is 65 cm in diameter and is unbreakable. It is the perfect fitness accessory for workouts at home or in the gym when you want to improve your balance and stability! It is also suitable for doing yoga and recovery exercises. This yoga ball is made of virtually unbreakable, dense PVC that allows for great support and control. If the ball is too stiff or too soft the effects on your core stabilizing muscle are compromised, but a hand pump to keep the ball at optimal pressure is included. You can use the fitness ball to train your core even if you use it while sitting at your desk. 1