[Advantages] The filter rod is made of high- fiber cotton. Strong water absorption to normal operation of the humidifier. The perfect filter replacement, when the filter is used up, there is no need to worry about the service life of the humidifier. [Cotton size] 0.32 inches (about 0.8 cm) (diameter) x 3.99 inches (about 10 cm) (length). The perfect sliver of portable mini humidifier 500 ml. If necessary, you can cut it to match other humidifiers. [Replacement] We recommend customers replace the filter after 3 months of use (depending on the usage and water ). [How to use] the cotton in water for 1 use to the completely wet.