Those hollow balls with 6 holes in them are part of the ferretrail. They are connector pieces so you can angle the tubes in different directions. I see a lot of pet stores that sell the ball with holes, but then no tubes and vice versa. On the Ferretrail box, however, there is a picture which shows it and how to connect this ball to the tubes. Is the person who makes ferret-proofed baby strollers on the FML? I can't remember where I heard about them. They sound neat! Do you sell them? How much are they and can we get them by Christmas? Happy thanksgiving. Charlene [Posted in FML issue 1387]