Like the other reviewer, this muffler doesn't slip like most; It's actually an interference fit which as you may know makes it quite difficult to install into the exhaust as all you can do is hit it with a hammer to try to install it. It should not be! I'm a certified technician and after 3 decades of working with cars and installing mufflers I've never had one that didn't slip. The sound on my 7.3 Power Stroke is just great! Deviates the sound over a straight pipe if you have a full blown 4" system with large air intake, turbo and no catalytic converter. With normal installation I would give 5 stars. But what would have been a 15 minute job turned into a frustrating hour job!