yeah it does actually, I've measured mine..
the diameter gets larger as it goes to the cannon, 3 inch from the cat to the hotdog, then 3.7 from hotdog to the square flange (longest section), then 4 inch after the last flange...
The HKS silent hi power for EVO, R34 GTT/GTR, silvia turbo are only 85mm all the way... and they're really quiet in comparison