2 Pcs 4 Inch Draft Blocker Backdraft Damper Duct Draft Stopper One-Way Airflow Ducting Insert Backflow Preventer Inline Fan Vent Deflector

【Product Contain】Package includes two backdraft damper with diameter of 4 inch/ 100mm. Please confirm the size before purchase. All dimensions are measured manually, please allow 1-3mm differences. 【Quality Material】The 4 inch backdraft damper is made of a Galvanized steel, the flap leaves are made of aluminum. 【Installation】The backdraft damper is installed by pushing it into the ventilation pipe as far as it will go. The position of the spring should be horizontal when the flap is installed horizontally so that it can be opened and closed optimally. This also applies to the vertical installation. 【Function】This airflow regulating backdraft shutter fits over the TD lip and is designed to improve ventilation by preventing air from re-circulating when the fans are not in use. 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. 【Wide Application】 These backdraft dampers can be widely used in ACs, exhaust fans, extractors, range hoods, heating ducts, vents and other residential, commercial and industrial applications