An office-type chair includes a back support having a support frame, front and rear shells, a cushion and a cover. The perimeter edge of the cover wraps around the side of the cushion and the front shell and is inserted between the front and rear shells to form a finished edge for the cover. The front shell may include a central flex section, and a lumbar pad may be positioned between the front shell and the rear shell and adjacent to the central flex section. One or more lumbar enhancement ribs on the front shell may augment the pressure distribution of the lumbar pad as it is vertically adjusted.