The DuraVent 3PVP-ADFF is a female flex adapter from the PelletVent Pro, a collection for biofuel vent system. This flex adapter is designed to connect the PelletVent Pro to BioFlex when relining a masonry chimney. With a measurement of 3 inches in diameter, this is only approved to be used with BioFlex and is made to be free from corrosion. This is a UL-listed product and is covered by DuraVents limited lifetime warranty.For your venting needs, you are assured that DuraVent can offer you the best and high-quality products. Search yours now at PlumbersStock.com.