Fairly sturdy once put together. Bought the XL for our 40 lb Doberman mix and he has a good amount of room to stand and plenty of room to stretch. He goes in and camps for a bit of time with the door open and shows no sign of damaging it to get out when the door is closed. One side appeared to come unglued prior to us assembling so the metal bars on that side kept falling out - appeared to be a defect since the other sides were a solid unit each. We were able to get the bars to stay in place once we finished by using the pressure to hold it in, but if we lift to move it they will fall out and need to be reassembled.