I got my rats yesterday . They are two almost 3 months old males: one solid blue/grey (Earl) and one blue hooded (Octavian) , pictures to come hopefully. They spent their night in the smaller of the cage I have for them. I really want to move them into the larger cage, however, since the smaller one is just barely big enough. The larger cage has bar spacing of about and inch, maybe just under. I put them in to see if they could escape and at first all they did was run around like maniacs. Eventually they got curious and started poking their noses through. I tried enticing them with treats and they were able to get pretty much their head through.. but the would get stuck and have to pull it back out. Im still watching them to see if they will sneak out (well one, earl is sitting on my shoulder chattering his teeth ) but what do you guys think? I'd rather be safe than sorry, but they are obviously a lot happier in the bigger cage.