Okay, so like a lot of people the ball didn't fit. See my pictures. As I first inflated the ball, I noticed it did not fit like so many others have posted pictures of. There's a good hand-width if not more between the bar and the ball and it didn't look like the pictures in the description at all. Disappointed, we turned to the reviews and noticed people having the same issue. Then I noticed something in the product description that was not in the instructions provided. Inflate the ball once, leave for 24 hours, deflate, let sit, rinses, repeat. So, I did this. I inflated the ball as much as that little thing would go. Soon it was letting out as much as as it was putting in, so I figured I got the ball as far as it would go and it wasn't the full size according to the pictures or the documentation stating its diameter. I let it sit for a while. Noticed the instructions. I deflated it and let it sit for a day that way. I inflated it once more after this and noticed that it inflated larger than it did the first time! Still wasn't big enough to match the pictures. I repeated the process. I let that sit for another day, deflated it and let that sit for a day, inflated it a third time and now I have the result in my other pictures posted. It touches the bar. It's still not up to full size according to the documentation, so I'm going to repeat the process once more. ALSO, the handpump was insufficient... I had to use a bike pump to get the ball up to a fuller size. We have 2 of these chairs and one ball inflated larger the first time than the other, still not enough but it was larger already. Just after 1 inflation/deflation cycle, it was the same size as the first ball after 2 cycles. So I'm going to put them both through another inflation deflation cycle and see if they get as big as the pictures seem to indicate. Now my problem is that the chair turns out to be TOO TALL for the desk we have... but that's my problem... THE REST OF THE PRODUCT REVIEW. It seems build well and is very light. It's all plastic save for the bolts and the bar. The bar is not adjustable for the most part, though I wish it was. Without the ball fully inflated, my child's calves hit the bar and he instead just puts his feet on it, which makes the bar push further away. It doesn't easily deform though but the plastic base could be damaged that way. The casters rolls well on carpet and the locks do work... on carpet. On hardwood the thing just slides all over the place just like anything made of plastic or wood or anything hard would do so, not really the fault of the design. If the wheels were rubber coated, they'd be fine. They're standard casters so I could get them replaced if I really wanted to. The thing installs easily. I'm not sure why the back uses hand operable bolts unless they intended for the back to be taken off and on enough to justify it? Or was it just out of wanting to make it as tool-free as possible? Regardless, it works as designed NOW THAT I KNOW HOW TO INFLATE THE BALL CORRECTLY. I'll also say that getting this product was the idea of the mother... I'm not really a fan of these balance ball chairs and it actually was horrible when I used an adult sized one (not from this product line). But with a back to the chair, it won't actually roll around, it might be nicer. My son just bounces on it a lot and wants to use it to climb with. Right now the ball is rather tacky, as in like it's sticky, but that'll fade. My other balance ball was like that it and it lost its tackiness after not too long. Hopefully the ball won't turn into just another play thing and the chair sits in the corner, empty and unused... but that'll be another problem entirely.