A. Applicable humidifier models: This is a replacement filter for humidifiers and is suitable for the following models: 3020, V3100, V3500, V3500N, V3600, V3800, V3850, V3900, etc. B. Quantity: It comes in a pack of 4 pieces. It's a cost-effective choice for home humidification. Increasing the air humidity during the dry season can create a comfortable home environment. A pack contains 4 replacement filters for humidifiers. Regular replacement can help prevent the indoor environment from becoming too dry. C. Perfect fit: The filter can capture minerals and pollutants in water, which helps prevent the formation of white powder. Its filter design has been improved to increase the moisture output. The filter material has been reinforced to achieve relatively high efficiency and a long service life. D. Tips for using the filter: It is normal for the humidifier filter to change color, and the specific color change depends on the water quality. To maintain good filtering performance, the filter should be replaced approximately every 1 - 2 months (the specific replacement time depends on the usage and local water quality), or when the performance starts to decline. If you find a large amount of impurities in the filter or a persistent odor due to poor water quality, you may need to replace the filter more frequently. E. Color: White F. Material: Wood pulp paper G. Dimensions: 20.5 x 13 x 2.2 cm H. Package contents: 4 pieces of humidifier filters I. Only the above-mentioned package contents are included, and no other products are included. J. Note: Due to light reflection and different monitors, the color of the item in the picture may vary slightly from the actual product. A measurement error of +/- 1 - 3 cm is allowed.