What Pat said about the nipple, I have gotten slim lines the same way, they can be used on too many different engines. Sometimes they come with the nipple and you may or may not want to use it.
I too have the Jtec muffler for my Brison 2.4 and when I got it the muffler hit the linkage or something?? I just phoned them and they sent me A little thicker stand off and it went right on. One phone call and problem solved.
I like there mufflers but there motor mount for the YS 1.40 was so outstanding and A perfect fit I can't see myself using any other brand. I say that now but what will I be saying when the rubbers wear out??