This custom designed aluminum heat shield is pre-formed to fit all Flowmaster 40 Series mufflers and attaches easily with included stainless steel muffler straps. Adding a heat shield to your muffler gives added protection in reducing exhaust heat radiated through the mufflers and also helps reduce interior noise. May fit all mufflers with an approximate case thickness of 4.00 to 5.00 in.es tall, 11.00 in.es wide and 13.00 in.es in length.