Penetraspheres

The magician shows six coloured balls and one colour is selected by a member of the audience. The magician places the six balls on the tray as well as a small glass which then has a larger glass inverted on top of it. Everything is then covered with a cloth. The magician reminds the audience what has happened and then, on removing the cloth from the tray, shows that the ball of the chosen colour has mysteriously appeared within the small glass, despite the larger glass still being upside down on top of it. This is a well made completely baffling trick.