The Replacement USB humidifier is a replacementpart for the Exo Terra Precision Incubator Pro withhumidity control. Connect the USB plug of the Replacement USB humidifier to the USB port located at the back of the LED display next to the power cable of the Exo Terra Precision Incubator Pro. Place the Replacement USB humidifier in the opening in the middle of the foam insert. To prime the Replacement USB humidifier, pour abit of water in the middle of the device, then turn itupside-down and lightly shake to remove excesswater. Then place the humidifier flat on the water soit will float and starts humidifying.