Give your rodent plenty of freedom of movement outside the cage without it escaping. Close the two halves of the Runner Ball very carefully. Make sure your rodent's paws don't interfere. Make sure the surface is as flat as possible and limit play time with the roller ball to a maximum of 20 minutes. Never leave your rodent unattended in the ball, and avoid direct sunlight! Choose a ball that's big enough to keep your rodent's back from bending too much.