Available from http://www.world-of-magic.co.uk
The mentalist shows a black envelope and states that inside it there are four kings. He asks a spectator to think of one of the kings and name it. Then the mentalist takes the cards out from the envelope he fans them and mysteriously the thought of king will be the only one turned face up among the others. But thats not all... the thought of king is the only one with a different colored back.
Very easy to do
The cards are poker size.