Sometimes simple is better and the 5500 basic design is an excellent example of simplicity at its best. It has an open grid back that conforms to your back for passive ergonomic support. Also features 2-to-1 synchro tilt, pneumatic seat height adjustment and angled adjustable arms. GreenGuard Indoor Air Quality Certified. | Office Star Products | | Silver Ion Technology Task Chair | Dillion Stratus | Best Buy