My office recently upgraded office chairs, and gave us a list of alowable chairs from GSA. Many of the newer, more active chairs were not listed, so I purchased a yogaball chair online and had it shipped to my office. I love it, it keeps my posture in check and I feel way more productive and healthy. Best of all, instead of the $400-$500 cost of a nice, supportive chair from the GSA list, it was under $100 including shipping! Several of my co-workers have purchased them and love the improvement they notice in their workday!