The measurements on these balls is circumference, not diameter, so the ball fully inflated will be far short of expectations if you’re expecting this to be diameter measurement. I got the 75cm thinking 30 inches is plenty high to use as a desk chair. Not the case. Lots of back and forth, recurving a replacement that’s even smaller than the original… absolutely not worth the premium price.

Not a good stability ball. It loses air fast (the pine doesn’t seat well. Also this 65cm is smaller than the 55cm I already have. Basically this ball sucks.

Outstanding quality and excellent for the price. Very robust.

At 6’6” and 230lbs I was unsure of size for my needs. Tha 55cm works well placed behind my back for wall squats and the size is good for two other Rehab exercises it is used with. The only trick; it came with no instructions but be advised you need the “cone” shaped nozzle to inflate and plugs to seal valve are included with the ball.