. The three pack is the PRE-FILTER pack for our Typhoon, Typhoon III, Compact, Dual, Monsoon, ED, Water Cop, and Neptune systems This is the filter replacement pack for about (90%) of all five stage RO systems out there. We ask you to change your pre-filters at least annually. (1) Sediment 10 Micron Poly Pro full size(1)Acid washed Coconut Carbon block 5 micron (1) Acid washed Coconut Carbon block one micronIf you have a five stage residential R.O.system you have a post membrane/storage filter, (the final filter) if you need to change ALL of the filters in your five stage R.O.system please consider our (4 pack) 4 pack.

The three pack is the pre-filter pack for our (Typhoon, Typhoon III, Compact, Dual, Monsoon, Ed, Water Cop, and Neptune)systems This is the filter replacement pack for about (90%) of all five stage RO systems out there. We ask you to change your pre-filters at least annually. (1) Sediment 10 Micron Poly Pro full size(1)Acid washed Coconut Carbon block 5 micron and (1) Acid washed Coconut Carbon block one micron.If you have a five stage residential R.O.system you have a post membrane/storage filter, the final filter if you need to change all of the filters in your five stage R.O.system please consider our (4 pack) 4 pack.