Our Yoga exercise balls are constructed from soft, elastic, and durable vinyl. They are similar to medicine balls, however, they are much larger and far lighter. These yoga exercise balls can be inflated or deflated by removing a valve stem and adjusting the air pressure. They are also known as Balance balls, Fitness Balls, Swiss Balls, Physio Balls, Exercise balls or PE Balls. They can be used in Yoga, Pilates, and fusion exercise programs to strengthen and firm abs, back and buttocks. They are extra strong and can stand 600 lbs. of pressure.