4″ reverse-cone megaphone muffler body with matching billet end cap. 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. Features hand MIG welding. 18 mm and 12 mm O2 ports with adapters and plugs. Includes mounting hardware and full heat shields. Made in the U.S.A..