Clear Transposition

The magician shows two empty paper bags and has them inspected. He then shows that in his right hand he is holding a plastic sheet with a card printed on it, while in his left he is holding a transparent plastic sheet. The magician now “dips” the sheets each, in one of the bags for only a fraction of a second. Incredibly when he pulls them out they are seen to have changed places. The effect can be immediately repeated making the plastic sheets instantly switch back again… just an illusion, or pure magic?

The idea of this trick is of Vincenzo Di Fatta.