Doepfer

I only have a limited number of Doepfer modules now, but they all seem 
to be pretty shallow (2 inches or so) behind the front panel.
What is the deepest module and how deep is it? Are any deeper than 4 
inches?
I'm trying to figure out how deep I need my case to be, but would like 
it to be as shallow as possible.
Thanks.
---Ben