Forever Flex 6" insulated stainless steel chimney liner 23' + long includes 3.5' piece too. New never installed. Sold by a chimney dealer. 6" ID 7.75" OD 316 SS with high temperature insulation between layers. New cost over $1000 I bought 31', but a forklift ate it in a warehouse. So I cut out the dent (see photo), leaving 23+' and a 3.5' piece. My bad luck, your gain.