Ball Storage Stackers are a convenient way to store stability balls. Simply fasten each stacker with the Velcro attachment to form a circular stacking ring. Stackers can be adjusted to hold a 45 cm to 75 cm stability ball. Sold in a set of three. Stability Balls are sold separately. Since 1986, Power Systems' passion for fitness has been fueled by our customers. Power Systems is committed to ensuring people have the tools to lead active lives with professional-grade products, cutting-edge educational materials, and elite customer service. “Power Your Potential” is the philosophy that guides everything Power Systems stands for.