The inlet is around 2.3" (if your turbo car can fit???) and the outlet is as big as the one shown in the pic posted by EG8.
And YES! the ITR DC5 muffler is exactly the one in this pic. Mine is a bit cleaner than this one.
Currently still in my car. You can actually see my car pic in the "Car Sale" forum here in 0~100 with title "JDM Honda Civic......".
Am selling only the muffler, not entire system. A bang for buck muffler! People normally opt for this muffler in optional to the famous Mugen Twin Loop coz the sound is quiet but giving good performance.