The noise is very slight. The turbo whine and wind noise are more noticable. It's not 100% quiet, but it is nowhere near as noisy as a Flowmaster. Also, it doesn't resonate in the cab like a Flowmaster. Realize you have to weld it using appropriate stuff to weld stainless, and you must also use a pair of 3.5" to 4" adapters. I had a local muffler shop install mine. I like how it is tucked up out of the way, but I did need them to put a slight bend in the tail pipe--you can't see it unless you look at the truck from the bottom--to get the tailpipe up and out of the way. The bonus is my tailpipe is higher off the ground than it was stock.
Here is Magnaflow's website:
http://www.magnaflow.com/ 
