The boxes are actually very thin and flimsy plastic that is not solid. The frames around the front and back are solid plastic. I was hoping for something I could store not only shoes in but all sorts of things, like some of the review said. When I put these together, the material is too flimsy to put slightly heavier objects in like charging cords and battery packs etc. or heavier crafting tools etc. The bottom line is these are not solid when put together correctly and the walls and floors of the boxes are not solid. I would not have bought these if I knew that. Everybody said they wish they bought more so I bought three sets. I’m bummed at the quality wish I hadn’t bought these.