Nice product for the price! Just got it yesterday and started using it at work today, but my lower back feels better already. I sit all day at work, and a good bit at night as well, which has led to almost constant lower back tightness and pain. After sitting on this for one day I already noticed a difference. Can't wait to see how I feel after using it longer!

I also had no issue inflating the ball to fit the cover. Some people indicated that the cover was too loose or big for the ball. I filled it yesterday to about 90% capacity right out of box. I took it into work and filled it a little more and it now fits like a glove (all photos of fully inflated).

Time will tell how the quality holds up. The pump seems really cheap, but did the trick and will not be used much I think. The cover is decent, although some seams do look a little suspect. But for the price I'm more than happy with my purchase, even if it doesn't last forever!

I'm 6 months pregnant (and my bump is very large at this point) and this is the most comfortable chair for me at my office. I'm about 5'6" and my knees sit at a perfect 90 degrees on this ball when fully inflated and adjusted to my height. I can keep my legs wider than on a normal chair which has been much more comfortable on my pelvis and makes it so the baby bump doesn't interfere with sitting. This has been so amazing that I am also getting one for at home while I watch tv instead of sitting on the couch! I love that the bottom has some sort of stability so the ball doesn't roll when not sitting on it!

I ordered this ball to replace the one I've been using as a seat at the office. The old one (different brand) has been great, but a hole has started to wear through the thick felt cover. So I decided to try this one.
Bad news first: It comes with a plastic foot pump to inflate the ball, which I found woefully inadequate (and it broke under use). However, using a small electric air compressor, I was able to carefully inflate the ball fully.
Good news next: Unlike what other reviewers experienced, I found the ball fills the cover completely (once fully inflated) and it looks and feels quite nice. I also like the quality and appearance of the cover. The seams look to be well sewn, and I feel this product is as good or better quality than my expectations... especially at this price point.
My mistake: Unfortunately, I failed to realize the old ball is 75cm in diameter and this one is 65cm... so it is significantly smaller. Too small for me to use as a replacement. The old one is just the right size for me. A ring base might raise it up a bit, but would take away from it easily rolling a bit, which is what i like about using a ball. So, I'll see if a shorter friend can use this nice ball chair and order another (75cm) for myself.

I recently started using a standing desk, which anyone who uses one will tell you, requires use of a cushioned mat under your feet to prevent undue foot pain/fatigue. My issue was that I still wanted the option to sit occasionally, and a conventional desk chair with legs - with or without wheels - would leave impressions on the mat and ultimately cause damage/tears from the weight of sitting, so I'd either have to use a compact enough mat that I could move it out of the way when I chose to sit on the chair (requiring extra effort at the very least), or find a seating option that wouldn't damage the mat. This was the perfect solution. Great quality cover, excellent fit - just follow the instructions regarding initial partial inflation and leaving it for a day before completing the full inflation.

EDIT: OK, this shouldn't need to be said, but even intelligent people can sometimes be careless and distracted, so: given that this is, you know, a ball - without feet or a secure base, please be mindful when you sit, and place your rear end on the ball with a reasonable degree of intention. If you don't place yourself squarely on top, the ball can easily roll right out from under you and leave you on your a**, particularly if you're using the ball on a hardwood floor, vinyl mat or any other reasonably slick surface, as opposed to a carpet/rug (although I don't think those more textured surfaces would make you immune to potential mishaps either, if you are careless/distracted when you place yourself down to sit...) :)

Es una buena pelota aunque algo difícil e de inchar