Flowmaster 80430402 - 40 Series Chambered Muffler

40 Series Muffler 409S - 3.00 Center In / 2.50 Dual 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.