I have had the Aeron chair for many years. The one I bought was used and I think it was on at least the second gas bottle as it was placed so low in the chair it almost scratched the floor. It stopped working so I decided to buy a new one. It suddenly occurred to me that I didn't have to buy the full-length cylinder. I might get one that's a little bigger so it sits a little higher and fits my 6ft 3in body a little better. This is the cylinder I bought. It works great. I want to be. He sits better in the chair than the previous cylinder. I am very happy.