Abstract: A chair base and post assembly for an office chair in which the base is formed of one piece of injection molded plastic. The base includes a central tubular hub and integral base arms which extend from the hub. A partially tapered socket extends vertically through the hub. A steel post tube is positioned in the socket and is supported to extend above the hub by a ring welded to the outside of the post tube, which ring rests on the top of the hub. A steel sleeve located in the socket near the top thereof and an internal surface formed as an internal surface of the socket at the bottom thereof provide annular surfaces which engage the post tube to stabilize it vertically. A plastic guide bushing fits inside the steel post tube at its top and receives the pneumatic lift cylinder to stabilize and guide it during its extensions and retractions.