Keyboard / Mouse Trays
When you work at a desk 40+ hours a week you need to be comfortable. The repetitive nature of typing can cause stress and pain in your wrist, forearms, and shoulders if your keyboard isn't set up right. A keyboard tray lets you set your keyboard at the proper height, which reduces the stress on your wrists.
The best height for the keyboard is at elbow height or lower. The angle of the keyboard tray should match the angle of your forearm so you can keep the wrist straight. For a low keyboard this may mean tilting the keyboard slightly backward.
To get the proper wrist angle you need an articulated keyboard tray, which can tilt forward and back. An articulated keyboard tray can adjust it's height and angle so you can change your posture throughout the day. Fixed-height keyboard trays are recommended when keyboard use is light.
If you use you mouse a lot, the tray should hold the mouse as well as the keyboard. Some models are also available with a soft wrist rest which helps distribute the pressure under you wrist.