This is a 3 filters set for a 20"x 2.5 Whole House Water Filtration Unit. The specifications of the set are as follows: 1 of Polypropylene Sediment– Sediment filter is often the first filter. The main function of a sediment filter is to remove large and fine particles from a drinking water, such as sand, dirt, silt, and rust particles. Removal of such particles allows for a better performance of all the following filters, such as Carbon Block or GAC filters.Lifetime: Replace two or three times a year, depending on the water quality. Micron rating: 5 Micron. Dimensions: 20" x 2.5" 1 of Block Activated Carbon– Block Carbon Filters are similar in their performance to that of GAC filters, being made of fine coconut shell carbon they also do remove odors and tastes of many organic compounds, chlorine especially. Lifetime: Replace two or three times a year, depending on the water quality. Micron rating: 5 Micron. Dimensions: 20" x 2.5" 1 of Granular Activated Carbon– GAC filters are well-known for their highly efficient reduction of chlorine taste and odor, as well as other taste and odors of many organic chemicals and volatile organic compounds. All GAC filters are made with high quality coconut shell carbon. Lifetime: Replace two or three times a year, depending on the water quality. Dimensions: 20" x 2.5" All filter is wrapped and sealed and meets NSF Standards and Regulations. FEATURES 20-Inch Sediment filter 5 Micron, 20-Inch Carbon block filter 5 Micron & 20-Inch Granular activated carbon filter KEEPS WATER FRESH - Reduces sediment, scale, rust, dirt, coarse sand, sand, fine sand, extra fine sand, silt IDEAL for a 20"x 2.5 Whole House Water Filtration Unit or any type of Water Filtration Unit with 20"x 2.5" housing FILTER LIFE 4 month or 12,000 gallons: Replace two or three times a year, depending on the water quality MEETS NSF STANDARDS and REGULATIONS