So we now offer two versions of the extractor. One made domestically with dual certified 304/304l low carbon stainless with visible weld marks or one made with 304 stainless with no visible weld marks. your choice. 304/304L dual certified stainless is a very low carbon "18-8" austenitic chromium-nickel steel with good corrosion resistance and superior resistance to intergranular corrosion following welding or stress relieving. The low carbon content limits the formation of harmful carbides to such an extent that this grade may be safely used for most operations of welded construction, and where the service temperature is limited to 800° F.