Roush axle back mufflers part number 421127. These fit 5.0 engines and also Shelby GT500. Constructed from 409 stainless steel for a durable long life, the Roush axle-back exhaust system features two unique chambered mufflers with 304 stainless steel 4" tips. The 4" tips are finished with a new chrome flashing process that is resistant to discoloration due to exhaust heat. On car for 2500 miles before selling vehicle. Perfect condition and have an aggressive sound to them. Paid $479 sell for $375.