This package of 350 AeroPress microfilters should last for months. The Micro-filter removes grit, unlike other press-type coffee makers. The filters are designed for use with the AeroPress, an entirely new way to make coffee. The AeroPress’s ideal water temperature and faster brewing yields rich flavor with lower acidity and without bitterness. Water and grounds are mixed together for 10 seconds, then gentle air pressure pushes the mix through a micro-filter in just 20 seconds.