"I brought this cage as a home for my four female rats. At first they were too small, and could fit between the bars (most rats can fit through anything as big as a quarter). Once they got bigger, they loved it. My only complaint is that urine collects on the trays, and requires daily mop ups (otherwise the smell is overwhelming). I had heard this before, and ignored it, but it is definately something to think about. But my rats love the multiple levels, and it is not so huge that it takes up a room."