Flap Exhaust Valves (Flap Stacks) Trapeze Hanger They are recommended for high

They are recommended for high moisture systems

and Angle Ring connections

not compatible with Heavy Gauge or airtight systems

Diameters are +/-  1/8 inch

Flap Exhaust Valves (Flap Stacks) Trapeze Hanger They are recommended for highA resourceful after the fan product, flap exhaust valves, or stacks, are designed to open, like bird wings, with the airflow and close when the system is not exhausting. The lightweight and balanced blades produce minimal resistance to exhaust. The design of the housing and blades channel rainwater away from the opening and allow it to drain without intrusion into the ducting. Available in 4" to 32" diameter (contact for custom sizes). Also known as