Question for Fluval C3 Users

Hello all,

I have a quick question for any C3 users out there. I'm looking at purchasing one, but I have rather specific space constrictions behind my tank. On the Fluval website they list the dimensions at 5" in depth - but I can't find any info on whether this is the entire unit, or the space needed behind the tank. Could someone advise on this, and maybe sneak me a measurement of how much overhang behind the tank there is?

Really hoping to be able to leave the world of internal filters behind (and my negotiations towards getting a canister filter with my lady wife are proving a bit futile at the moment).

Thanks!