I bought the small for my budgie, which was surprisingly big, and i didn't think she would like it because it was so big, but at first glance she loved it and immediately started playing with it unafraid of the size. it has pieces of wood, cuttlebone and little shreds of paper that she loves to shred, I don't mind the mess she leaves at the bottom of the cage because I know my little budgie is very happy. :D