Prevent cold drafts and take control of the fresh air intake for your heating appliance with this 5"Ø airtight damper register. Its simple mechanism effectively blocks outside air when the appliance is off, reducing heat loss. • Sturdy steel mechanism for enhanced durability • Airtight damper prevents cold air from flowing back when the appliance is not in use • Built-in positioning shim for precise installation based on wall thickness • Compatible with certified wood and pellet appliances requiring a 5" fresh air intake