Set of 4 USB-connected 92mm fans. With holes in all four corners, they can be attached to any location, such as a breeding shelf. Perfect for animal racks or indoor LED plant racks. These are pure fans, so they do not emit cold air. With a diameter of 9cm and a thickness of 25mm, they provide a strong airflow. The brushless motor is very quiet and consumes very little power. Originally designed as PC fans, they are built for long-term continuous use and are highly durable. They are not rechargeable. You don't have to worry about battery depletion or degradation, so you can use them with peace of mind.