A spectator's bill, which he signs or marks, is placed inside a 9 silk along with a rubber band. The silk, rubber band and bill are then placed inside a glass. The glass is covered with an aluminum tube. A second glass is placed upside down in a second aluminum tube. Before you can blink the opening of the second glass is now covered with the 9 silk which is held in place by the rubber band and the signed bill in trapped inside the glass under the silk!
Yes - the spectator removes the band and the silk to discover that it is indeed his signed bill!
It doesn't get much stronger than this!
Great for the bar magician!