These mufflers start as round 4-inch tubes, then bell out to 4.5-inches, for an aggressive and classic design at the rear. The muffler tip is then rolled to give them a clean, finished look. Internally, these NH mufflers have a spun and louvered baffle, but only for 8-inches. This is done in order to produce an aggressive, bark. At the end of the baffle is a trumpet shaped inner tip that works in harmony with the belled end, creating a unique look. There will also be a quieter core option for those who enjoy the look, but don’t hate their neighbors.