4 Pack, The Culligan S1A whole house sediment water filter replacement cartridge filters scale, rust particles, sand, dirt, & silt for basic filtration. The filter life is 4 months or 16,000 gallons. The filter has a 20 micron rating, pleated paper, For use with model #HF-150, HF-160, HF-360 and most standard size sediment filters. It also includes a change reminder sticker.