I bought this product thinking I could attach it to my hamster's cage and let them run in and out to give them some extra space. The next day I came home, one of my hamsters had mysteriously disappeared. She just climbed out of the fence. I didn't think she could because the bars are vertical, but she did. We found her, but after quite some searching. That was pretty much the end of that, but once I decided to just watch them in the pen. They can't get out if you're watching them right? Um no. Wrong. I turned my head for about 1 second(not exagerating), and turned back to see one of my hamsters out of the cage and on the floor. Do NOT buy this product. It is a waste of time. If you really want extra space, buy something with a roof.

Pros: it is big

Cons: hamsters can easily escape