Just wondering what the best wheels for rats are and what would be good for them. I see the saucer wheels all the time. Used to have a wheel for my rats, but never heard or saw them use it, but I want to try again. The original wheel was lost in a couple of moves and now I'm looking for a new one. I'd like something that's quiet and won't hurt their backs or hurt their tails, preferably! I'd like to hang this on their cage so they can run on it when I'm not home or even while I'm sleeping if the wheel is quiet.