This is a HIGH QUALITY unbelievably durable box for the serious breeder. It won’t bend, shake, lift or breakdown and is held together with carriage bolts. The framework is so sturdy you can lean on it and even sit on the wall panels. It is made of a Heavy Duty Plastic frame and FRP Plastic panels (like wall paneling, only plastic). This is not the corrugated stuff, it’s a safe, hard, strong and durable. Breeds of all sizes and strengths have used this box without fail. The insulated raised base floor panels keeps heat in and helps control the box temperature. You will love the strength, durability and quality of this box. You won’t find a better made Whelping Box.