The yellow cap on the tube fits entirely in the yellow cup. They really had to work to lift the tube up out of the cup and off to the side. The twist tie is the only thing that kept the tube from dropping to the bottom of the cage. Of course, any water in the tube ended up in the cage tray. We have always had two water bottles in the cage, so they aren't in any danger of not having water. The other water bottle is the more conventional tube and ball type. If we want to keep using this style of water bottle, I'll have to figure out some way to mount the bottle on the outside of the cage. Kids.
Our curiosity is piqued, and now I really want to get the video camera set up to see what is going at at night.