APEC Water Systems FILTER-SET-ESPH High Capacity Replacement Filter Set For Essence Series Alkaline Reverse Osmosis Water Filter System Stage 1-3&6 APEC Water ESSENCE series FILTER-SET-ESPH is for ROES-PH75 1st stage: 5 micron polypropylene sediment filter to remove dust, particles, and rust 2nd & 3rd stage: 10 micron extruded Carbon block filters to remove chlorine, taste & odor 6th stage: 10 inch high purity US made ph+ calcium carbonate alkaline inline filters with quick connect APEC extruded solid carbon block filters far surpass GAC filters in performance and absorptive capacity; in addition they do NOT leak carbon fines