Contains electro-static charges and is highly effective to trap fine dusts and particles even below 0.3 micron.
The filtration efficiency is at least 92%. Typically each pair of filter last for 1 week in polluted cities. (based on 1 hour use per day, 6 days per week).
Filters packed in one ziplock plastic bag. This is the econormic general purpose filter, high value for money.