UCCU is a pocket in your shirt where you can drop one or several cards and retrieve them as easily.
It's a topit specifically designed for playing cards.
This way the spectator can shuffle the deck as much as they like. Their selected card will always be on top when they hand you the deck again.
I'm sorry but a video can not clarify if the effect is impromptu or not.
Since you're hesitating to answer the impromptu question, I'm gonna assume it's not.
Next guess: Since it's not a crimp, do you add wax, fanning powder or any other substance to the chosen card?
btw I'm still waiting for a response about my effect :P
If the time limit has been extended you should let me know, also if there's a thread in the premium section by now.