Seat is fabric upholstered over foam that is applied to a molded polypropylene liner. Back is a frame of molded glass-reinforced nylon with 100% polyester mesh fabric. Torsion mechanism consists of two flat torsion springs captured at both ends by steel bushings welded to the backrest supports. Five-blade 24” base is injection-molded glass-reinforced nylon with high-impact thermosplastic double wheeled casters.