BORLA XR - 1 Raceline products are the choice of todays hottest drag and oval track racers. Featuring a patented uninerrupted - flow design and multicore technology. BORLAs XR - 1 mufflers actually outflow a straight piece of pipe in repeated testing. XR - 1 race products are light weight and constructed of high quality austenitic stainless steel for track - tough durability. They meet the strictest noice requirements and use sound absorbing stainless steel pcking to protect against burnout. Hands down, BORLAs XR - 1 Raceline offers the best balance of sound and power.