I'm not sure why you haven't already received a reply. This is an excellent effect that works so simply that it leaves them scratchiing their heads. It is a "card trick" that doesn't use cards - not playing cards anyway. It uses hotel key cards, so mentalists who prefer not to use playing cards in their act can use these very familiar items without suggesting slight of hand. In my opinion the beauty of this effect is in its simplcity. I haven't had anyone come close to figuring this one out.