Solve Series Reactiv Back Task Chair, Supports Up to 300 Lb, 18" to 23" Seat Height, Midnight Seat, Charcoal Back, Black BaseHeight- and width-adjustable arms for upper body support.The ReActiv hexagonal design is molded from flexible thermoplastic elastomers and contains dozens of intersecting nodes which flex independently and move with your body, delivering continuous support while allowing air to flow for lasting comfort.