Peace be upon you I am offering for sale electronic GM truck mufflers that were previously installed on a Sierra model 2012. The muffler sound is smooth when closed, and when opened, its sound is pleasant and moderate, not annoying, and it gives a nice tone. When you accelerate and the valve is open, the sound is a bit loud. Note that the mufflers are not hollowed out, so as not to bother anyone with the smell of carbon, and that's all.