The magician displays a miniature deck of cards and has one selected by a spectator. The deck is spread face down on the table, but it's somehow shrunk
The spectator looks at their selection, let's say it's the Six of Diamonds. When the spread of cards is turned over, all the cards are the Six of Diamonds! To finish, the mini spread is turned over to show a Six of Diamonds long card!to half its original size!