Ergonomically designed for maximum comfort and long lasting service with a backrest rocking mechanism and stylish aluminum base to set this chair apart from the rest. Pneumatic height control raises and lowers the chair quickly and easily. Features include molded foam seat and back cushions, polypropylene seat and back shells, height and depth adjustable backrest with spring-adjusted rocking mechanism, dual wheel casters and a 23" diameter polished aluminum base. Seat cushion is 19"w x 17"d x 3" thick. Backrest is 16"w x 14"h x 2 1/2" thick. Office model height adjusts from 16" to 22". Drafting model includes CK49 height extension kit and adjusts from 23 1/2" to 29 1/2"