"I purchased the 600 CM rolling den, but actually received the 500. I took it to the local Pet Co, they acknowledge the mistake and immediately exchanged it for the correct size. I am glad that I had kept my original purchase order (on line confirmation) as well as the paper work that came with the product. All in all I am very happy with the "den" itself, and very pleased that it will roll which is definitely a bonus with a large breed dog."