Thank you all very much for your help and advice/links.
That has helped me. It is the Rolly wheel Lucy was trying to use. Lucy is trying to use it more but, still doesn't quite do a full circle. I had a funny idea that maybe the wheels that came with cages were not too great. Thank you for the advice that if I wanted to buy a flying saucer I would still have to get an upright wheel too and thank you for the advice to Plastikote a wooden wheel if I got one. I had a cage many years ago that had a lot of wooden parts to it and it got ruined/stained mainly by water.