3" diameter system. Adding this muffler to the 11933 Axle-Back system and the 60622 Mid-Pipe assembly will achieve the "Touring" sound level or it can be used with the 11934 ATAK axle-back system and the 60622 Mid-Pipe to make a quieter version of the ATAK system. Use ONLY with BORLA systems. It is Not designed to be used with competitor or Original Equipment systems. 3" diameter part. Built from premium T-304 stainless steel, superior to T-400 series (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.