Bevco 7500 Ergonomic Standard Chair, 18" Dia. Adjustable Chrome, Reinforced Plastic Base, 21" to 31" Height Adjustment, Black Durable, contoured polyurethane seat and back with ventilated ribs for lasting comfort and support Easy-to-use pneumatic seat height adjustment with "lifetime" cylinder guarantee Sturdy five legged base in reinforced plastic with mushroom glides or tubular steel with rubber cushioned metal glides Fully adjustable back with heavy duty back bracket Metal components have scratch resistant top grade baked enamel finish