Proper venting of gas fireplaces is essential. This Type B gas vent pipe by Dura-Vent is easy to install and simple to use. It comes with a twist lock system which makes for secure, easy to install connections. The construction is two layer with an inside liner made from .012 aluminum and an outer wall made ouot of .018 galvanized steel. The vents listed by the UL and ULC with a 25 year warranty. Five lengths available.