COMPATIBLE: This PDC51CV1 humidifier demineralization cartridge compatible with For Vicks Ultrasonic humidifiers: V4600, V5100 and VUL575. USE WITH TAP WATER - A Demineralization Cartridge for humidifiers may be especially helpful in areas where there is hard water. Use it to help capture the minerals in your water before they are released into the air. REDUCE THE WHITE-DUST - This PDC51V1 Demineralization Cartridge for humidifiers aims to reduce mineral (calcium & lime) buildup and white dust caused by hard water in ultrasonic humidifiers. Reducing calcium and lime buildup may help extend the life of the humidifier and facilitate routine maintenance. LONGER LIFE - Use a replacement cartridge as necessary; every 2-4 weeks or 15-30 fillings under normal use or when the humidifier has not been run for an extended period of time.<br><br>Please note: the physical slightly color difference or difference, does not affect the use, please do not mind, thank you! Material: plastic colour: blue<br><br>Package Contents: 4 x Ultrasonic humidifier Filter<br><br>Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.