Flowmaster 8042541 - 40 Series Chambered Muffler

40 Series Muffler 409S - 2.50 Offset In / 2.50 Center Out - Aggressive Sound 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 409S stainless steel and fully MIG welded for maximum durability.