Stepped headers merge into a true reverse-cone megaphone muffler, 1-3/4″ headpipe steps up to 1-7/8″ into the collector to increase flow and improve performance, Removable spiral-core louvered baffle included, 4″ muffler body with billet end cap, Includes mounting hardware, Heat shield included, Includes 12 mm and 18 mm O2 port plugs, Made in the U.S.A.