Chrome. Comes with a 4" diameter body that bells out to 4.5". These are perforated core slip-on mufflers that are, some say, too loud and nickname them 'Neighbor Haters'. But for the Loud Crowd these are the slip-ons that will truly bring life to the bike! The sound is loud & low and fully different from the shrill sound of drag pipes due to the 2" constant velocity baffle design with stainless mesh and high/density bonded fiberglass wrap. Note: Very loud.