This is a blockbuster trick, but it relies on two slights that require a fair amount of practice to
perform well.
The first crucial slight, unfortunately is very poorly taught. It is, in
fact, almost entirely obscured in the performance videos. Moreover, it is performed DIFFERENTLY by
the two instructors, and neither demonstration is thorough. Rather, one instructor just says that it
is referenced at length by another instructor's trick.
The second slight is discussed at
length.
Also, I was disappointed that the full Penn and Teller trick - which I assume is
based on the same principle - was not included, but left as an exercise for the viewer.