There are far better, more discrete ways to switch a deck
Thats why people invented pockets....
Seriously though, the deck shell allows you to switch decks 'right in front of your spectators!!' but in my opinion it really is too bold and is just a matter of time before you get caught. Spectators are not idiots.
I would not waste my money on a trend which these deck shells seem to be. In the end it is about how casual you are and how much attention you place on the deck at the moment of switching.
To be honest, you don`t need a deck shell to accomplish this
