All dimensions stated are length x width x height. A Pack Of 20 x Extra Large Double Wall Cardboard Boxes 24"x18"x18". A very common size used in the removals industry, and the most popular double wall box size that we distribute. This is the largest size we recommend for removals. A solid x-large size it is also good for heavy items, files & folder storage, warehouse dispatches, and for use as postal boxes through courier networks.