I really like this box! The assembly was not easy, it took 2 of us but  we put it together quickly between us. If I was writing the instructions I would do one side first, then the back, then the other side. I was almost impossible with the back on to get the sides to clip in. cat just jump in the top and out, they haven't figured out the one way door in the front yet. The opening and box are roomy enough for my big kitty who is 22 pounds and very tall.