I ordered this muffler to replace the stock muffler on my 2005 TrailBlazer with a 4.2 inline six. I asked my local muffler shop to weld it for me as the inlet and outlet diameters of this 2.5" ID muffler are basically the same as my truck's factory 2.75" OD pipe. This muffler definitely gives my I6 a great sound without making it too loud, which is great considering I have two neighbors with young children. BTW, my resonator (a reservoir behind the rear axle next to the spare wheel) is also removed and between 1800 and 2350 rpm I do hear a certain hum, but I've gotten quite used to it by now.