VRSF downpipes are hand crafted from mandrel bent SS304 grade stainless steel and our CNC precision machined flanges are also constructed from billet 304 grade stainless steel. All VRSF products include a lifetime warranty as well as our “No Hassle” satisfaction guarantee (including fitment). All M135i & 335i models produced up to 07/13 require the 3.5″ version of this downpipe. M135 and 335i models produced after 07/13 require the 4″ model of this downpipe. All M235 and 435i models require the 4″ version of this downpipe. Please feel free to contact us with the last 7 of your VIN if you need help determining exactly which version of the downpipe your car requires.