Travel ESP Cards Blue & Red (Gimmicks and Online Instructions) by Paul Carnazzo - TrickE. S. P. Cards, also known as Zener cards are a great tool for mentalists and magicians. These are now available in either BLACK backs, or RED and BLUE backs. Travel ESP Cards are the most portable ESP cards ever made! They are 100% plastic, the same dimensions as a credit card but they are SUPER thin. The BLACK set includes ten marked cards, a double backed card and a two way double faced card. The set takes up about the same space as 3 credit cards.