Black Mountain Products professional grade stability balls are Exceptionally durable exercise balls designed for gym, office and home use. Each Pro Series ball is designed to hold 2000lbs of Static weight and is Anti-Burst resistance up to 1000lbs of Static weight. Black Mountain Products gym balls can improve your core strength, balance and overall agility. Each exercise ball is designed with dense walls for the ultimate support and durability for any use. Size options 45 CM (5' and under) 55 CM (5' to 5' 6 tall) 65 CM (5'6 to 6' tall) and 75 CM (6' to 6 5 ) and 85 CM (6' 5 or taller).