Used as pre filter in both carbon and reverse osmosis undersink units. These are inexpensive ($10) usually polyspun and recommend change every 6-12 months, depending on water quality. This is the case in older homes with sediment in pipes, however most homes need only replace every 12 months. This cartridges plays an important role as it removes fine sediment ensuring the carbon cartridges does not get clogged and able to removal all chemical contaminants.
Pleated sediment cartridges are also available when heavy sediment is concern. Sediment can be washed off the pleats to maintain acceptable flow rate over the 12 months.