Uh.. wow. I had no idea such a thing existed, and now I do and kinda wish I didn't!
Not sure about as actual cards for tricks, but as a meme for fun speculation the possibilities for teenage sniggering are limitless: Boob to Wallet Any Boob at Any Number Twisting the Boobs The Ambitious Boob Boob in Shoe ...?
Oh, oh dear. I was trying to think up a pun about double-backed boobs and now my mind has gone to the strange place. Time to switch off the computer and go get some fresh air....