Personally, I don't think degus should be put into a ball. It is better to let them run around freely in a playpen or a degu-proofed room (i.e. one where potential escape routes are blocked and wires are covered (to prevent electrical shock when they test the wires for chewability). Degus feel very restricted being in such a small space of the ball, particularly when they do not have the freedom to exit the ball when they want. In addition, their eyesight is not great to begin with so they are able to see very little clearly through the ball. In addition, when they run into things when they are in the ball, it is like being in a car accident. I prefer to leave the ball open within their playpen. That way if they want to go into the ball, they can. But they have the freedom to get out when and if they want to get out of the ball. Finally, they usually pee and/or pooh in the ball and so are rolling around in it. How would you like to be rolling around in your pee and/or pooh?