GaiamBalance Ball Chair Stool, Half-Dome Stability Ball Adjustable Tall Office

Great chair -- however, everytime I stand up, I need to pump up the ball again. First thought it was my weight. But when my child sits on it, it does the same. So not just me. There seems to be a fault/leak somewhere. When the ball pumps up - pumps up full, but then slowly deflates.When full and sitting - it's great. The chair is high enough for me to sit at where I do not have to change the height of my (standing) desk, when I'm too tired to stand. Fits neatly under the desk and out of sight when not in use.