Unique Amazing Exercise Ball 21.6in/55cm CHAIR REPLACEMENT** The exercise ball can also be used as a replacement for a chair at work or home. Perfect to help increase balance, strength and flexibility, great for kids and adults LONG LASTING* Anti Burst Professional-grade materials used with thick walls for ultimate support and durability. Great value for money LOSE WEIGHT* Flattens tummy, slims thighs and lifts butt with proper and regular exercises ALLEVIATE BACK PAIN* For a person with back pain, the exercise ball can be used for a variety of purposes. Also great for quads, hamstrings, calves, shins, glutes, pecs and hips EASY TO USE* Ideal for beginners, intermediate and advanced users. As an introduction to exercising on the ball, it is often recommended that one simply sit on one for 30 minutes a day and bounce lightly, continually finding and maintaining balance on the ball