HOW TO INFLATE YOUR GYM BALL TO A SAFE SIZE
Fully inflate your gym ball using a tape measure to check the diameter. As a guide, here are the maximum diameters of our different gym balls: Size 1 = 55 cm, Size 2 = 65 cm and Size 3 = 75 cm. Finally, sit on the ball and check that your knees are at hip level. If not, adjust the inflation level accordingly.
P.S.: You can also use the pump to inflate your soft ball or textile instability cushion.