Draft Blocker - 4'' Inch Backdraft Damper Duct - Draft Stopper - Backflow Preventer - Inline Fan Vent - Vent Deflector (4'' Inch)
- The backflow flap opens and closes automatically at low air volumes. It has a smooth-running spring and an internal foam strip to keep the blades from rattling and can be installed horizontally or vertically.
- Back draught valves can be inserted into ventilation ducts which are flexible or non flexible. Cannot be used with plastic ducts as the sizes are different. Size: 4'' Inch.