Function: It can effectively block impurities,, in the air, improve the, and keep the air cooler clean The replacement filter is suitable for portable USB air purifiers, which can be absorbed quickly and effectively Replacement frequency: It is recommended that the filter be replaced every 2-3 months to avoid excessive use of product bacterium : No need but your air cooler does not work, you only need to replace a filter and you can use it again, allowing you to breathe for and wind and protect the for health of your family : This replacement filter is specially designed for second generation USB air coolers, without any special tools, it only takes about 2 minutes to complete, giving you a cool and cooler