Borla XR-1 Raceline products are the choice of today's hottest drag and oval track racers. Featuring a patented uninterrupted-flow design and multi-core technology, Borla's XR-1 mufflers actually outflow a straight piece of pipe in repeated testing. XR-1 race products are lightweight and constructed of high quality austenitic stainless steel for track-tough durability. They meet the strictest noise requirements and use sound-absorbing stainless steel packing to protect against burnout. Hands down, Borla's XR-1 Raceline offers the best balance of sound and power. This muffler has an inlet diameter and outlet diameter of 3.5 inches each and a case size of 15 inches.