I've only used it a few times. My huge hamster and my smaller rats can squeeze through the bars really fast. My larger rat can climb up to the top and then climb down to get out. No matter how many toys and treats I put in there, all the pets want to do is get out. They're so occupied with escaping they don't even play! Maybe with the cover it would be fine for large enough animals, but I don't think it's worth the money.