Headpipes Ppd R Bk Fl 17+Pro Chamber HeadpipesFor the Milwaukee Eight motor, Cobra modified their PowerPort by enlarging it to become a pulse chamber that accelerates exhaust scavenging to produce the kind of power riders expect The round shape, bulging from between the heat shields gives a clue to the real power potential it offers Stock H D mufflers will not work with this head pipe because of the stock mufflers internal construction. Most aftermarket mufflers will fit