Agreeing with other reviews, the muffler only makes it a little quieter. But what I did in addition, was fitted the original muffler to the end of the new muffler using Iron pipe nipples and bushings press fitted together.
The two together is significantly quieter. However, you can't do anything about the generator noise itself.
Still overall better.
The only thing that should be included with the Muffler is a speciaity 90 degree angle #3 Phillips head. The mounting screw connection is so tight it takes some ingenuity to tighten. The outside screw I replace with a bolt but you can't get a wrench or socket on the inside one..