CFS GRANULAR ACTIVATED CARBON CARTRIDGE — 10 X 2.5 INCH A direct replacement for WHKF-GAC and WHCF-GAC, in the standard slim line size that fits most 10 inch housings. GRANULAR, NOT A PRESSED BLOCK Granular activated carbon fills the cartridge as loose media rather than being pressed into a solid wall. That puts more carbon surface in contact with the water and lets it pass with less pressure drop than a block of the same size, which is why granular suits positions where flow matters. It reduces the chlorine taste and odor that make water unpleasant to drink and cook with. What it does not do is fine particle filtration. Granular carbon is a taste and odor stage, so if your water carries sand, silt or rust, run a sediment cartridge ahead of it rather than expecting this one to do both jobs. KNOW WHICH CARTRIDGE YOU HAVE The same housings take carbon block cartridges as well as granular ones, and they look similar in the box. WHKF-DB1 and WHKF-WHWC are blocks. A block filters finer and restricts more; granular flows better and polishes taste. If you have been buying by the housing number rather than the cartridge number, check what you are pulling out before you order. WHAT IT REPLACES WHKF-GAC and WHCF-GAC, and the same size and position as GAC-10, 155109-43 and CC-10. It measures 9.75 by 2.5 inches and seats in most 10 inch slim line housings. WHEN TO CHANGE IT Carbon exhausts rather than clogging, so it stops working before the flow drops. Change on a schedule instead of waiting for a sign, about every three to six months on typical municipal water. Run water through a new cartridge for a few minutes before use to clear loose carbon fines. Compatible replacement cartridge. Part numbers are for reference only.