The Screw Fix Increaser to Chimney Liner connects single wall stove pipe to a Flexible Flue Liner where the flexible flue liner is 1 inch greater in diameter than the single wall pipe. This 316 grade steel adaptor has a threaded metal connector allowing it to screw onto the flexible chimney liner. The 45mm tail single wall end connects to your vitreous stove pipe. So easy to install, no fire cement, no self tapping screws to secure it, just an easy thread that screws directly onto the liner to provide a secure and tight fit.