I first went with the 2.75 Inlet, 3.5 Outlet. When I went to put that one on it was a little to big, where you would clamp it down. I then cut the larger piece of the exhaust system from the truck, right at the outlet. The factory exhaust has a larger tip, about 4 inches long. I sent the first one back, then I ordered the 2.5 Inlet, 3.5 Outlet. (Part Number 500374) When I received the new one, I had to spread the clamp a little wider. The tip looks great. A little modification does not hurt.