You may know it as SAF-T Pipe! It's made from 22 gauge .030 cold roll steel with 100% laser or advanced resistance-welded seams. What does this mean? It means it's a thicker pipe than most hardware store brands & it guarantees a completely sealed seam = no smoke or flue leakage! It is designed for interior use only, to vent coal or wood burning appliances. Available in a full range of parts & sizes, individually wrapped and packaged for shipping!