APEC Water ULTIMATE Series FILTER-SET is for RO-45, RO-90, RO-PH90, RO-PERM, RO-PUMP, and compatible with all 10" standard industry reverse osmosis water filter system . Includes (1) sediment and (2) carbon block filters to protect and extend the life of the RO system 1st stage Polypropylene sediment filter to remove dust, particles, and rust 2nd & 3rd stage extruded carbon block filters to remove chlorine, taste & odor APEC's extruded solid carbon block filters far surpass GAC filters in performance and absorptive capacity; in addition they do not leak carbon fines.