The BOK 120 duct fan by MMotors has a diameter of 120 mm and a connection size of 100 mm, and is designed for continuous or intermittent ventilation of small and medium-sized domestic, sanitary and commercial premises. An automatically closing flap (accessory) is provided, preventing the entry of cold air and insects when the fan is not working. The device has a built-in silent electric motor with rolling, double encapsulated bearings (NSK Japan), which guarantee 30,000 hours of trouble-free operation of the device when installed in a horizontal or vertical position. The body, impeller and flap are made of aluminum alloy or specially selected plastic. The housing of the electric motor is made of aluminum alloy or heat-resistant material, guaranteeing good cooling and increased fire safety.