Borla's CrateMuffler? is the world's first muffler purpose-built to optimize the sound & power of crate and custom built motors. The mufflers are directional. The outlet can be identified by the mounting bracket welded to the endcap. The directional design provides custom sound, tuned for each engine family and will dramatically reduce, or eliminate drone on specified applications. 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. Precision computer-controlled CNC manufacturing ensures an accurate fit and best of all, Borla stands behind every CrateMuffler? with a Million-Mile Warranty. Just what you'd expect from the world's most experienced (and most winning) exhaust brand.