Borla 2005-2010 Mustang GT - Dragster headers downswept with 2 1/4 O.D. XR-1® Racing Exhaust XR-1® Racing Dragster Headers Features lightweight high quality austenitic Mandrel-Bent Stainless Steel Tubing in 2-1/4, 2-3/8" and 2-1/2" primaries. Add an XR-1® Standard Size Collector/Muffler or a BORLA Merge Collector for a winning combination.