There are 4 holes on the back of this wheelchair tray, just by fixing the safety hooks and screws on the armrest of the chair, it can be installed and removed easily, no cumbersome installation and removal procedures, no other tools Specification: Product Type: Wheelchair Accessories Product Material: ABS Tempered Plastic Product Size:55 31 cm (21.7 12.8 in) Cup Groove Diameter: 7cm (2.76 in) Product net Weight: 1.3 kg Suitable Wheelchair Seat Width: 40.6-50.8 cm (16-20 in) Package includes: 1 Wheelchair Tray Table Other Accessories Note: 1. Do not sit or place overweight objects. 2. Only wheelchair trays are sold and do not include wheelchairs. 3. Due to lighting and display reasons, there may be color differences between the real object and the photo, please refer to the actual object. 4. The above data is for reference only, the size is measured manually, there may be 1-3cm error, please refer to the actual product, thank you.?Wide Desktop?: The extended and wider desktop design provides users with a wide enough range, providing ample storage space for laptops, cups, mobile phones, pens, business documents and personal items, and is an excellent tool for wheelchair users to eat, read, write, work, etc. ?Excellent Material?: It is made of thickened ABS plastic steel material, and the back grid shape is densely covered with bulges, which endows it with strong load-bearing capacity and is more stable and durable. ?Stable Design?: The edge of the tray has a special raised design of about 1 cm, in order to prevent other small objects such as pens for writing and tableware for eating from rolling off the edge. There are 2 circular grooves on the tray for easy placement of water glasses. ?Wide Compatibility?: Fits most wheelchairs with a distance of 16-20" between two armrests. And fits wheelchair tube dia :0.85"-0.9". And a pencil slot to prevent rolling off and keep your items secure while supporting your arms and posture. ?Ergonomic Design?: It is fixed with nuts and brackets made of fine steel, which is not easy to slip and is extremely stable. Our wheelchair tray can also be used as a support device to help users maintain posture and support arms. The table board can correct the user's sitting posture.