A. Wide application - This 4 - inch embedded duct fan can be used in places that need a large amount of ventilation, like homes, offices, warehouses, restaurants, shops, shopping malls, grow tents, greenhouses, etc. B. Overheat protection - The motor runs at a relatively low temperature and generates little heat. It is equipped with an overheat protection device. When the motor overheats, the contacts break, providing fault protection and additional insurance. C. Airflow performance - It uses a sleeve motor, which runs quietly and is energy - efficient. The rotation speed is 2800 revolutions per minute, and the airflow is 140 cubic feet per minute (CFM). D. Customize your HVAC system - You can equip one or more fans according to the size of the space to customize the circulation system. It can make air pass through the activated carbon filter, long - section ducts, or grow light reflectors. Use the fans to exchange dirty air with fresh air to control temperature or humidity and cool down the reflectors. It is considered safe and environmentally friendly. E. Non - insulated flexible aluminum ventilation duct - It is reinforced with built - in steel wires for relatively long - lasting performance. F. Voltage: 220 volts, 50 hertz G. Input power: 25 watts H. Rotation speed: 2800 revolutions per minute I. Air volume: 140 cubic meters per hour J. Operating noise: 30 - 35 decibels K. Dimensions: Diameter 93 mm, height 78 mm L. Aluminum ventilation duct size: Length 1 meter M. Color: Black N. Material: Metal O. Product size: 93 x 78 mm P. Package contents: 1 duct fan, 1 aluminum ventilation duct. Only the above items are included in the package, and other products are not included. Q. Note: Light reflection and different monitors may cause the color of the item in the picture to be slightly different from the actual product. A measurement error of plus or minus 1 - 3 cm is allowed.