Home Improvement: Especially suitable for inserting into dryer duct. Perfect for use in bathrooms, garages, sheds, campers, stopping inflow of air from AC units, range hood extractors, heating systems Easy Installation: The duct damper opens and closes automatically, allowing only one-directional airflow. The damper blades open only in the outflowing air direction when the shutter is installed. The duct valve for 8-inch duct best installed in a horizontal position and inserted fully into the duct. This also applies to vertical installation Premium Material: The casing of the shutter is made of galvanized steel sheet. The dryer vent valve blades are made of aluminium. The shaft and spring are made of stainless steel Great for Home Use: The inner rubber seal is used for better tightness and for noise reduction. The outer foam sealing strip provides good tightening and fixing of the backdraft damper inside the duct. The back draught valve can be inserted into a non-flexible metal or plastic duct directly, but for flexible duct you must use steel duct clamps to secure the backdraft damper Warm Prompt: Please note the diameter of this backdraft damper is 7.9" and it can be fit in a 8" diameter pipe or hole easily. If you have any questions about our backdraft damper shutter, our professional customer service team is here to assist you, Manufacturer: FRESH SPEED