20″ x 4.5″ Full-Flow GAC Filters, Pentek Big Blue
These are Big Blue, full-flow 20″ x 4.5″ GAC filters by Pentek. They are constructed of granular activated carbon (GAC).
GAC is positively charged and, therefore, able to remove negative ions from the water such as ozone, chlorine, fluorides, and dissolved organic solutes by absorption into the activated carbon.