The DuraVent 4PVP-WTI3 is a wall thimble air intake kit that is fit for your biofuel venting system. Under the PelletVent Pro collection, this allows fresh air for combustion to enter through the wall thimble without cutting a second hole into the wall. This kit includes an insulation ring to reduce air infiltration, a flex hole, and clamps. The wall thimble measures 4 inches in diameter and the flex measrues 3 inches. It is applicable for a double wall construction and is considered a UL product.As a technological leader in providing quality and innovative products in the venting industry, DuraVent continues to give its customers the convenience to avail their products in cooperation with PlumbersStock.com. Search the one you need now only here at PlumbersStock.com!