The Humanscale DS Keyboard Tray Mechanism Arm provides for a second swivel point at the point where the mechanism meets your Humanscale Keyboard Tray, making it easier to shift your position and maintain proper placement as you work. The DS mechanism is ideal for situations where users sit and face different angles of a workstation. Humanscale DS Keyboard Tray Mechanism Arms come standard with a 25" track, although other track lengths are available. Please note this is only the Humanscale DS Keyboard Tray Mechanism Arm only. If you are looking for a full keyboard tray system, you'll need to view our selection of complete Humanscale Keyboard Trays.