Mild steel. At just under $1200 for it couldnt go past it. Xforce Exhaust Systems Ford Falcon BA-BF XR6 Turbo Sedan Models Turbo Back Single 89mm [3 1/2"] Sports System with 4" 102mm Single Dump Mild Steel Recomended for high performance applications Part No. Item Description EM-F6-02-FB dump pipe assembly 4" ES-F6-02-CATB hiflow metal cat 100 [cpi] EM-F6-02-F2 connecting pipe [3 1/2"] EM-F6-02-C front muffler assembly MF-MP01-3.5 rear mufler assembly Notes Direct fit [gaskets & bolts included] some slight modifications may be required for perfect fittment. Imported Direct Fit [Note: slight mods may be required] Gaskets and Bolts Included Interstate customers contact us for freight charges [discounts may apply] More Images Click Here Check Availability Before Ordering