I beg to differ with some of the statements above.

Close to three years ago when I started selling gas engines the muffler were failing on a daily basic, Stacks falling off and ends blowing out.

Through a lot of research I found a company in China to make me some replacement muffler and after about a year with no failures in them I had them to make me mufflers for different brand engines.

In the last two years not one has been returned from failure, I did give a refund on a set of mufflers for a DA 120 because the customer was told by someone at DA if they used them they could possibly over heat there engine and void there warranty, That is hog wash and they know it, The mufflers have a 25mm tube and a 25mm inlet, So how could this cause a engine to over heat. ?????

Milton