DuraVent Pellet Vent 3 in. W x 3 in. L Silver Steel Wall Thimble (Pack of 2)PelletVent is a venting system for stoves and inserts that use multi fuels (including wood pellets, corn, cherry pits, switch grass, coffee husks, walnut shells, soybeans, wheat, sunflower hulls, rapeseed and sugar beets) or oil fuel. The DuraVent PelletVent wall thimble is used as a pass through for PelletVent pipe through a wall and is adjustable to match various wall thicknesses. Compatible with only wood pellet burning stoves, this wall thimble is