"RBM assumed you were describing a 4" square box as:
http://www.grainger.com/Grainger/wwg...shtml?ItemId=1...

(this one has the side mounting bracket he described) with a raised
cover as:
http://www.grainger.com/Grainger/wwg...shtml?ItemId=1...

which seemed to fit your description. He suggested a single gang
mudring
for a concealed 4" square box as:
http://www.grainger.com/Grainger/wwg...shtml?ItemId=1...

A 4" square box gives you a lot of volume. "


That's what I have in my basement, where I use surface mount wiring
components. That would look terrible inside my bathroom wall. I was
asking fi there is a way to center it and have it completey inside the
wall.