316Ti .006 stainless steel square chimney liner. Air and water tight. This flue liner has 7 ply seams, rated number one in the industry for strength. Our square chimney liners are UL listed in the United States UL1777 and ULC365 in Canada. They are made of the very best, hand selected, prime stainless steel material available on today's market. The sizes listed are square O.D. (outside dimensions) and pricing is per foot. See our Square Liner Conversion Chart.