APEC FILTER-SET US MADE Double Capacity Replacement Pre-Filter Set For ULTIMATE Series Reverse Osmosis Water Filter System Stage 1, 2&3 APEC ULTIMATE high capacity pre-filter set is USA made and built to last 2x longer than other brands 1st stage polypropylene sediment filter to remove dust, particles, and rust 2nd & 3rd stage extruded carbon block filters to remove chlorine, taste & odor Compatible with APEC RO-45, RO-90, RO-PH90, RO-PERM, RO-PUMP, RO-Hi, WFS-1000 and all other standard size under counter reverse osmosis systems