The chair collapsed and would not go up or down after about 5 months. I called Staples because the chair was still under warranty. They told me that they do not replace the chair. They can only send a replacement for the part that had failed. Not knowing which part had failed I agreed to accept a replacement piston. When it arrived there were no installation instructions nor they they tell me how to remove the existing piston. It's very comfortable but don't expect it to last. Plan to replace it & not to repair it even if it fails in the first year.
I tried almost all of the office desk chairs at the store. To me this was the most comfortable and supportive. There were some that were very comparable but they were more than twice the cost of this chair. For the money I liked this chair well beyond any other they offer. Also it was pretty simple to assemble.