[Duct Diameter: 3.9 inches (100 mm)]

[Duct Diameter: 4.9 inches (125 mm)]

This is a vent rattle that can be mounted on the outside or on the wall of the duct fan. Are the outer vent covers worn? Please replace the ventilation cover when you change the fan. Wind shutter ventilation air pressure opens the shutter and closes when the fan is stopped. Since it is normally closed, there is no need to worry about rain or insects coming in. Duct diameters are available in 3.9" (100mm) and 4.9" (125mm). Please confirm the diameter of the duct you currently use in your fan before purchasing. Duct must be connected with commercially available aluminum tape. Mounting screws not included. Please prepare screws to match the mounting base. Not for kitchen fans. Because it is made of resin, it may deform when exposed to high temperatures. Please refer to the picture for size and other information.