Show the audience a small box with two balls inside. Next hand the box out to a spectator challenging him, in ten seconds, to manage to put one of the balls on the right side, and the other on the left side. He will never manage, and you will have won the bet.
• The box measures cm 7(l) x 2(h) x 2(w).
• An ideal gadget to give as a gift after your show.