4.5" diameter muffler bodies taper to 4" at the front, 4.5" machined aluminum, thin-line tips, 3" diameter muffler cores for superior performance, Acoustical engineering developments allow an incredibly deep sound because of intense, class-leading resonance absorption and prevention, Use proprietary materials with specific acoustical dampening and thermal insulation properties, The frequency and location of the perforation patterns in the cores creates significant sound scattering in the mid frequencies, which helps to enhance the low frequency tones, Made in the U.S.A.