Hand TIG-welded stainless steel construction. 1-3/4″ headpipes step up to 1-7/8″ into the collector to increase flow and improve performance. 4″ diameter straight can 11″ muffler body includes matching aluminum end cap. Removable spiral-core louvered baffle features an aggressive sound. 18 mm and 12 mm O2 ports with adapters and plugs. Partial heat shields and mounting hardware included. Made in the U.S.A..