Improve your core and your balance with the Power Systems VersaBall stability ball. This training ball promotes proper posture, increases lower back mobility, and builds back and abdominal strength. Constructed of a high-quality, professional-grade PVC material the Versa Ball won't pop if punctured. Instead, the ball deflates slowly, significantly reducing the risk of injuries if a puncture occurs while in use. The VersaBall is easy to inflate and includes a tape measure that makes it easy to tell when you've added the right amount of air. This Versa Ball measures 55cm in diameter and is recommended for users from 5'1" to 5'7" in height.