4″ reverse-cone megaphone muffler body with matching billet end cap. 1-3/4 head pipe 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. 18mm and 12mm O2 ports with adapters and plugs. Includes mounting hardware and full heat shields. Made in the U.S.A..