A very cool gimmick from Joker Magic -- it allows you to hold a card case, wave a jumbo card over it, and when the card passes, the card case has changed into something else -- best ones (in my opinion) are: changes into a wad of hundred dollar bills; or changes into a different color deck, or a miniature deck; or the case vanishes, leaving an uncased deck of cards.
You can change it into your phone, though most phones these days are larger than a deck of cards -- so although you can still use your phone, it is a bit more angle-prone than other items which are the size of the card case.
You probably guessed how this works, and I will tell you, you're right. But the gimmick is very well made -- in fact, it is exposed in the first photo of the jumbo card's back. (yes, there is a card case hidden there!)
This is an earlier version of the effect, with printed instructions. (recent versions include a DVD, but this one does not. On the other hand, recent versions cost about $50, so you can save 50% if you know how to read printed instructions)
Complete as issued with jumbo card, box gimmick, and original printed instructions.