PelletVent is a complete venting system from DuraVent for stoves and inserts that use oil fuel or multi-fuels (including wood pellets, corn, cherry pits, switch grass, coffee husks, walnut shells, soybeans, wheat, sunflower hulls, rapeseed and sugar beets). The Double-Wall Chimney Pipe Increaser transforms a 3 in. stove outlet to a 4 in. outlet and features a twist-lock connection for easy installation. Its double-wall, air-insulated design offers superior performance and reliability for long-term use. For added durability, PelletVent seams are factory-sealed on all elbows, tees and fittings.