set of 3 replacement filters for Aquasky rot-3, Aquasky rot-4, Aquasky rot-5 and Aquasky rot-6 - This replacement filters are only for the ( C.T.A.D Long Filters - 3 stage reverse osmosis systems ) you can send a picture of your water system through using smart phone fof confirmation before placing an order, we will text you back in less than 10 minutes to confirm witch is correct replacement for your water system, it uses sediment pre-filter to reduce sediment particles before the membrane filters out impurities larger than 001 microns. GAC post filter treats for taste and odor. You can find and order all your filters at once in our replacement kit STAGESSTAGE 1 – Sediment Pre-Filter – Replace Every 12 Months STAGE 2 – RO Membrane CTA 14-35 GPD – Replace Every 24 Months STAGE 3 – Carbon GAC Post Filter – Replace Every 12 Months