Unique Design, Persistent Ventilation Capability; Window direct-exhaust, need no duct Make 24 hour's ventilation possible Large air volume, low noise High-efficiency axial impeller. DPT-B/ Split Duct Ventilation Fan Series Flexible and exquisite, high efficiency The mini cube fan body suitable for variety of installations; Sirocco design makes it with the features of high pressure and low noise Intersection angle air supply, easy to install, high pressure. Invisible construction, fresh and beautify your life.