This optional resonator is used when additional sound reduction is desired. It is designed to be used with the BORLA Cat-Back systems 140750, 140750BC, 140750SB, 140751, 140751BC, 140751SB, 140741SB. It is Not designed to be used with 140597 or the original equipment exhaust system. 3" diameter part. Built from premium T-304 stainless steel, superior to T-400 series knockoffs (such as 409), to give you the absolute best in performance and durability. Ultra-smooth mandrel bends ensure maximum flow & power, and precision computer-controlled CNC manufacturing ensures an accurate fit. Best of all, BORLA stands behind every connection pipe with a Million-Mile Warranty. Just what you?d expect from the world?s most experienced (and most winning) exhaust brand.