Filtration. Single, Twin and 3 stage water purifiers are used for water filtration. Comprising normally on a 3 stage water purifier that contains a Sediment filter. GAC (Granulated activated carbon filter ) and a carbon block. Coming in 4 sizes. 10” x 2.5” and 10” x 4.5” jumbo. 20” x 2.5” and 20” x 4.5” jumbo.