The wizard inserts three large white cards in an envelope with the window. Although the cards are clearly seen through the window when they enter into the envelope, and even if they are never removed from public view, the cards magically transform into playing cards. It will seem as if the cards were actually printed with magic.
 
In addition to playing playing cards, you can also use this effect to print cards for birthday with a personalized message.
 
The effect can be performed face to face with a spectator, but the cards are big enough to be seen by large groups of people.