It allows for stability when using a mouse. When not in use it can be turned completely sideways allowing an easy access to the chair. An interesting feature of the pad is that the pad can be easily lifted and completely removed. The pad is our most affordable armrest. It's a great addition for keyboard use as well. Two units can be installed (one on each side of the keyboard) to give complete support to forearms. The armrest is extremely portable and installs simply and quickly. It can be disassembled in seconds and can easily be carried in a briefcase or computer bag. The pad has been extensively tested for strength and we are confident that under normal use, it will not crack or break. Size: 11.4*5.5*0.8 Inch, weight: 0.55lb colour: black Material: ABS Package Contents: 1 * Board 1 * Clamp 1 * Screw Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.