3M Adjustable Keyboard Trays are designed to be the best possible adjustable keyboard trays on the market. They have a full range of height and tilt adjustability to bring the keyboard and mouse to optimal level for comfort. 3M Adjustable Keyboard Trays have a unique side arm design which allows for greater knee clearance, stability, and user-friendly adjustment. The 3M AKT200 is for work surfaces 24 inches or deeper. The 3M AKT200ST is for work surfaces less than 24 inches deep.