First of all, regular envelope and special envelope are different. And spectators clearly can see
the difference. Also immediately knowing the principle.
It works almost as the window envelopes
- you cannot give it to spectator for examination before or after putting in the drawing. You just
can handle it freely (both sides), but only in your hands.
And, of course, 2 minor things
together - the size is big and you must put business card in exact way.