JEGS Flowpack Bullet Mufflers are the same high-flow design used in our SRT8 Challenger and 2010-up Camaro SS Cat-Back kits. These mufflers feature an aluminized steel case with a 409 stainless steel perforated inner core for high flow and long life. The stainless inner core has an expansion joint that allows it to expand and contract with heat to prevent cracking which is common with most similar mufflers. The packing material in this muffler is a long strand high-temperature fiberglass to deaden sound and stand up to the test of time.