I joined David Stone's lecture and I saw the routine by using a special card.
The routine is:let spectators choose a card(I guess that he forced the card), the card is 3 diamond, and then he take the K club and write down the prediction at the back.
As he show the prediction(is 5 diamond), the spectator say that he get the wrong answer and show the card to David Stone.Finally, he shake the prediction such that "3" changed into "5".
I would like to buy this product!!Where could I buy it??Thx for answering.


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The effect you're talking about is
NUMBERGROUND from french magician Michael CHATELAIN.
You can get it there :
http://www.bdli.fr/product_info.php?prod......02e21a9f