High quality heavy duty shelves for being plastic. You WILL need a mallet and the easiest way to assemble is to take needle nose pliers and bend in the sides of the part of the “leg” you insert in the hole to allow some give. (Last pic is how it comes, then I showed the pliers and how you bend in the sides to make it easier to fit into the imperfect plastic cast) Otherwise assembly would be very frustrating. Once assembled though, they are great! Pay attention to assembling so they can link together if you’re assembling multiple to stand side by side, I didn’t and I was bummed. They are able to fit together like a puzzle for extra sturdiness.