2 Box of 2 (total of 4) high quality, reusable Aquarium Filter bags Suitable as a holder for other mechanical or chemical Aquarium Filter Media Micron Aquarium felt filter bags are very effective at trapping particulate matter in the thick wall of the bag Designed to provide fine ‘polishing' of fish tank water that is already low in particulate matter (mature aquariums) These 10. 5-Inch long Aquarium Filter bags for Red sea's Reefer and max-s aquariums will also fit any standard 4-inch filter bag holder. you will receive a total of 4 filter bags