I have a warehouse of 1500 banker boxes. I need to stack them high to make good use of space so I have 18 on a shelf and 18 on the top of the shelf. I bought these shells for the ones on the top shelf. I bought just one set (contains 6) to test them out and I wasn't disappointed in them! Sturdy! They fit Amazon banker boxes really well and you can buy just the six shells which gives you two rows of three, then you can stack two more boxes on top. It's not so bad to move two boxes, but moving five in a stack stinks. I'll buy more!It is not obvious from the descriptions but this part includes six shell boxes (not twelve or fifteen) and no internal storage boxes. It was not a big surprise based on the cost and weight but just not clearly defined (unless I missed it somewhere).