The 5500 basic design of this manager's chair is an excellent example of simplicity at its best. The open air-grid back with built-in lumbar support conforms to your back for passive ergonomic support. The black mesh seat is thickly cushioned for enhanced comfort. Functions include pneumatic seat-height adjustment from 18-3\/4" to 23" , 360-degree swivel and 2-to-1 synchro tilt control with adjustable tilt tension. Angled arms with soft pads are height-adjustable. Heavy-duty, angled nylon base has oversized, dual-wheel carpet casters. Seat size is 20-1\/2" wide x 21" deep x 3-1\/2" thick. Back size is 20-1\/2" wide x 18-1\/2" high. Distance between arms is 18-3\/4". Professional Dark Air Grid Back Managers Chair is also Greenguard Indoor Air Quality Certified.