Ergonomically designed for long-lasting service and extra comfort. Features include pneumatic height control, polypropylene seat and back shells, a height and depth-adjustable hinged backrest with spring-adjusted rocking mechanism, dual wheel casters and a 24" diameter reinforced nylon base. Seat cushion is 18"w x 17"d x 2" thick. Backrest is 16"w x 14"h. Office model height adjusts from 19" to 23". Drafting model includes CK49 height extension kit and adjusts from 26??" to 30??". Optional armrests available on page 22.