Ergonomics Desk Extender Tray, 20x9.5 Inch Table Mount Arm Rest Shelf, 90° Foldable Keyboard Tray Platform, Clamp on Computer Arm Rest for Desk, Suitable for Office Desks, White Our upgraded small desk arm rest is equipped with adjustable double C-clamp, compatible for desks with thickness up to 4.7 inch. The outer sides of the extender tray are rounded, protecting users from scratches. Pre-assembled, the manual knob supports fast installation and disassembly, realizing multi scene conversion and use. : It is 90° foldable to save space and be easy to store. Sturdy structure can securely hold up to 33 lbs with the size of the support board 20x9.5 inch. Please make sure that your desktop does not exceed a thickness of 4.7 inch. And the distance from the aprons to the edge of the desk should be larger than 2 inches. : This product employs premium MDF sheet and anti-rust steel sheet with coating, environmentally-friendly, durable and without odor.equipment support, etc.