Humidifier Sticks Cotton Filter Sticks Refill Sticks Filter Replacement Wicks for Portable Personal USB Powered Humidifier 7135mm (10pcs) Filter Sticks Size0.28(Diameter) x 5.31(Length)inch. You can cut it to fit with your diffuser/humidifier if necessary. ReplacementWe advise our customer to replace the filter after 3-4 months use (depending on usage and water quality). How to UseTo see a better performance, we advise user to soak a filter stick to be wet completely before inserting to the humidifier. AdvantagesProlong the service life of diffuser: if the diffuser/humidifier is always complete-blocked or half-blocked, it will become hot and become broken easily, we highly recommend you to use water-solubility essential oil and clearwater. Our ServiceIf you have any question or concern, pls don't hesitate to contact us. We will reply you ASAP!