The Culligan 20 Micron Sediment Replacement Cartridge is a Resin-impregnated cellulose cartridge. Fits HF-150 & HF-360. Medium-fine (20-micron) sediment filtration: sand, silt, dirt, rust particles and scale particles. Pleated for increased surface area and strength. Level 2 Extra Filtration. Filter life up to 4 months or 16,000 gallons. Not recommended for use with non-treated well water supplies.