1. Innovative technology: Uses electrostatic filter material to effectively capture airborne particles larger than 0.2μm; filtration efficiency for 0.5μm particles exceeds 95%. 2. Extends filter life: Captures dust, pollen, bacteria, and other airborne contaminants, helping protect the main filter element and reducing its exposure to pollutants. Can extend the air purifier’s main filter life by over two times, reducing replacement frequency and cost. 3. Improves filter performance: The pre-filter design helps maximize the service life of the original filter, supporting optimal performance as intended by the manufacturer. 4. Low air resistance design: At an airflow velocity of 0.5 m/s, pressure drop is as low as 3.5 Pa—minimal impact on airflow performance. 5. Compatible with Xiaomi Mi Air Purifier 1, 2, and Plus models. Can also be cut to fit air conditioners, windows, or electric fans. Filtration targets include soot and PM2.5 particles. Designed for use as a pre-filter in front of a HEPA filter to help extend HEPA filter life. Soft, non-toxic, odorless, and washable up to two times—avoid vigorous rubbing. Suitable for modified air purifiers, household air conditioners, fans, circulating fans, exhaust fans, and similar devices. Color: White Material: Cotton Size: 70 x 30 cm Package includes: 40 pieces of filter cotton