Description: There are some invisible marks in every piece of the back of card. And you can see the marked cards clearly when wearing perspective glass.It's suitable for all kinds of poker games, for example,Blackjack,Omaha poker, Texas hold'em etc. Use for: Contact lens Perspective glassess poker cheat gamble cheat Other Modles: Crient 714 Hoyle Lancer Opel Rado Paris NO.772