Made out of high quality 304 stainless steel these "shorty" headers are designed as a direct bolt-on to the factory exhaust system and as a direct bolt on when used with our short mid pipes. They will bolt on to the existing factory or after market cat-back system. ALL BBK exhaust headers are pressure tested to ensure leak free performance. Each Stainless Steel short tuned length exhaust header for the 2005-2009 Mustang GT has been designed and dyno tested at the BBK headquarters in Southern California to Maximize performance.The headers are Pn 16125 and have a retail cost of $ 459.99 Contact BBK at (951) 296-1771 www,bbkperformance.com