Borla XR-1® 2005-2010 Mustang GT - 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. Application: Dragsters and Altereds.