This Selkirk Flexi-Liner B Vent Adapter is made from 2 ply 3003 alloy aluminum construction and is used to connect to any brand of Type-B vent pipe. These chimney liners and adapters are designed for use for existing listed factory built or masonry chimneys and vents for all Category I listed gas-fired appliances equipped with draft hoods and/or appliances with Type-B gas vent which burns either natural gas or propane. The Flex Liner chimney liners and components are UL 1777 listed and should be installed in accordance with manufacturer's instructions.