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" High Purity US Made pH+ Calcium Carbonate Alkaline Inline Filters w/ Quick Connect APEC's extruded solid carbon block filters far surpass GAC filters in performance and absorptive capacity; in addition they do not leak carbon fines.