Adjustable from 15 3/4" to 20", Polyurethane Seat and Back, ErgoTilt Control with Seat & Back Tilt, Plastic Control, Upright & Hinge Covers, Shrink Wrapped Lever Shafts, SS Screws & Threaded Studs Pneumatic Cylinder with plastic bellows and bottom cap with filter, 24" dia. Nylon Base, 02S Plastic Dual Wheel Casters with SS Stems. - 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.