The Smart Stability Balls are self-guided for users at all fitness levels. They feature 13 exercises that are printed on the ball for easy reference. This yoga ball can help improve your posture and reduce back pain. Smart Stability Balls are also a great way to increase your core strength and flexibility. So, if you're looking for an inexpensive way to improve your health, then a stability ball may be the perfect solution for you! Exercising with a stability ball can be a fun and challenging way to work out your entire body. These exercise balls come in a variety of sizes, so it is important to choose the right one for you. Once you have your ball, you can follow these exercises to help improve your strength, balance, and coordination. Three sizes available, each are burst-resistant (PVC construction) and includes a pump. The Yellow ball has a 55 cm diameter and is recommended for those who are 5'4" or under.