S-Type CrateMuffler For Small Block Chevrolet High Output 350/ 383/ 406 V8.Borla(r)'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