[Cotton swab 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 that customers replace the filter after 3 months of use (depending on the usage and water quality). [Advantages] The filter rod is made of high-quality fiber cotton. Strong water absorption to normal operation of the humidifier. The perfect filter elements replacement, when the filter elements is used up, there is no need to worry about the service life of the humidifier. [How to use] Please soak the cotton swab in water for 1 minute before use to make the swab completely wet.