40 Series? Muffler; 2.5 in. Offset Inlet/Center Outlet; Case Dimensions 4 in. x 9.75 in. x 13 in.; 19 in. Overall Length; Aluminized Steel; Durable Fully Welded 16ga Aluminized Steel The Original 40 series muffler delivers an aggressive exterior and interior tone. If you re looking for that original Flowmaster sound this is the muffler is for you. Constructed of 16 gauge aluminized steel and fully MIG welded for maximum durability. This product ships in approximately 1 days