Polyurethane Seat and Back. Plastic Control Cover minimizes exposed metal parts. Cylinder with Plastic Bellows and Bottom Cap, Nylon Base with glides or casters with Stainless Steel Stems, Nylon Footring (Bench Height chairs), Stainless Steel Screws and Threaded Studs. Seat Range is approximately 23" to 33". Optional Nylon Coated "T" style base and Nylon Coated Footring. Standard Ergo Tilt Control with seat/back tilt and pneumatic height adjustment. Optional BackTilt Control with back tilt and pneumatic height adjustment. - The Harsh Environment 9000 Series incorporates a polyurethane seat and back to handle the harshest of environments. To resist corrosion, special attention has been taken to cover or coat all exposed metal including the control, back upright and handles. All threaded knobs and caster stems were made out of stainless steel. These and many other innovations make this the chair for most corrosive and wet applications.