It's 12cm square. I will send it by mail, so it will be shipped flattened. It's made of a sturdy material, so I don't think there will be any problems after opening it. Please only purchase if you understand this! It comes with a removable mat-like item at the bottom. "Near unused" → I intended to use it as a pet hideout, but I only washed it with water and haven't used it for its intended purpose. It would be good for hamsters, reptiles, or other small animals.