I will post some pics tonight so you can see how hideous it looks. I ordered it because their website specs said the Tip was 4 inches. My 2009 GMC 6.2 factory exhaust was 3.5 OD with a 4 inch tip, I liked that look.
The 14 factory exhaust is 3.5 like my 09 was the only difference is the goofy flapper valve and the exhaust is reduced to 3 after the resonator on the 14, and like others have pointed out the 14 exhaust is pretty stout. My accessory guy at my GMC dealership recommended adding the 22" Magnaflow and deleting the flapper valve from the beginning, but I insisted I wanted the 15318 kit..wish I would have listened to his recommendations.