Yeah, Bill, I grew a bit since I saw you :-)... It is a 4x5 Chamonix camera that this back is being made for.... 4 1/2" square plates make use of the internal dimensions of the rear standard. I could have gone a tinny bit larger, but the frame for the GG and the plate holder would be a LOT harder to make and be strong so this is it for now. Once I get the guts of the light trap varnished and painted, I"ll paint the inside of the darkslide track as well. Then after making the rear door, I will test how light tight this thing is with printing paper cut to size by leaving it in bright light for a while. Should be a good test. Fingers crossed it needs no further tweaking!