The treat tube is a wonderful foot toy for small-large beaked birds that encourages exploration and challenges the avian mind. Place a treat or pellets inside the tube and watch your parrot attempt to get it out of the hole (or sly dismantlers may try and unscrew the cap- both are right, clever bird!).
Small is good for small-medium beaks; Large is good for medium-large beaks. (Use your best discretion with medium beaked birds- Congo and Camaroon Greys may get a large, whereas Timnehs may get a small)