This is wonderful for rats, they can not climb it and you can get inside and play with them. I have two girls and two more on the way and my oldest girl can jump the side, of course she hangs there not knowing what to do next so I have plenty of time to get her. I would highly recommend this product for rat owners. Just make sure you do not leave them alone in it because if they can they will jump. Rats are like children you can not take your eyes off them for a moment. I have left them alone while I change their cage and they were fine, Scarlett just gets the scent of things and decides to jump, not all the time though. So I would recommend this for rats over the play pens made of bars...hello they can climb...lol