The PelletVent Pro Chimney Adapter is used to transition between 4" PelletVent Pro to existing chimney such as 6" DuraTech, DuraPlus, or DuraPlus HTC. Requires a DVL/DuraBlack Chimney Adapter to fasten into support box or wall thimble. PelletVent Pro is a venting system designed for stoves and inserts that use wood pellets and oil fuel.