Extension pipe 60691 is used to adapt BORLA Cat - Back systems 140798, 140798BC, 140843, and 140843BC to Super Duty trucks with an Extended Cab with Short Bed (6' 9) 148 Wheelbase. EXCEPT vehicles with dual rear wheels. 3.5 ID Inlet, 3.5 OD Outlet, 8.5 Long. Includes 1) 3.5 clamp. Built from premium T - 304 stainless steel, superior to T - 400 series knockoffs (such as 409), to give you the absolute best in performance and durability. Precision computer numerical control (CNC) manufacturing ensures an accurate fit. Best of all, BORLA stands behind every extension pipe with a Million - Mile Warranty. Just what youd expect from the worlds most experienced (and most winning) exhaust brand.