Exercise balls generally harmless to human body made of PVC material, between 65~75 cm in diameter, hollow structures, inflatable you want to use.
Standard diameter sizes 75 cm fitness ball, 65 cm. Choose according to height, more than 1.60 meters tall ball of selection criteria, selection of 1.60 m 65 cm. Use hands to hold the ball, feet clip is the best choice. Endurance 100 kilograms of the ball, hands down feeling very flexible, soft and comfortable quality.