It look like a 4" inlet/outlet,I could look up all the exact specs in the Go-Dan catalog for you if you want them.BTW,are you from the WNY area? I recognize the BFI logo's.
Is there any chance that this happened in Florida? Maybe even Brevard County (Cocoa Beach area)? Saw a dump truck rolled. Looks like he was trying to do some drifting heading to the dump off of SR520. Guess the Nittos wouldnt hook back up and he had to use the little known braking technique "roll-it-into-a-ditch-at-rush-hour" haha