DuraVent 4 in. D Steel Pipe Adapter (Pack of 2)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 is designed for use with wood pellet burning appliances and features twist lock connections for fast, easy installation, enabling transition from a 3 inch to