Rat/Small Animal Box

A box for a small caged animal, such as a rat. It is designed for cages with about 15 mm spaces in between the horizontal bars and 12.5 centimeters between vertical bars. As you can see in the pictures, my rat is very tight in it and barely fits, but for some reason enjoys it. The other two rats owned by other family members completely ignore it (they might climb on top of it at the most), so maybe it's because of my scent.