The DuraVent Direct Vent Pro Attic Insulation Shield is required for any vertical venting when the chimney pipe is passing through an attic space. The Attic Insulation Shield will prevent any insulation or debris from accumulating around the vent pipe. The Attic Insulation Shield will provide 1" clearance to combustible material. Includes the base plate, extension tube, and storm collar. The shield is able to adjust from 11" to 20" tall depending on the amount of insulation in the attic space. If the attic space is too low to accommodate the Attic Insulation Shield, the vent pipe must be enclosed in a chase.