Here's the specs from the website:
The best part of the case in the hidden sliding compartment at the back of the phone. It saves so much time when I'm searching for my card or cash in the bottom of my bag (which we all do) as I know that's where it always is.
I guess the only downfall to this fabulous feature if my phone is stolen, (touch wood it isn't) both my card and any cash is gone too. But hopefully that doesn't happen and I don't have to stress too much about it.