-Yearly Filter Replacement Kit for Hydro Guard HDGT-45 Reverse Osmosis System (50 GPD RO Membrane Sold Separately)1 Year Filter Replacement Kit for the Hydro Guard HDGT 45 Reverse Osmosis System (RO Membrane Sold Separately) INCLUDES: STAGE 1 1x Sediment Pre Filter (HDGT SED5) Replace Every 12 Months STAGE 2 1x Carbon Block Pre Filter (HDGT CB5) Replace Every 12 Months STAGE 3 0x (RO Membrane HDGT TW50Sold Separately or with Replacement Kits YSM HDGT 45) Replace Every 24 Months STAGE 4 1x Carbon Post Filter (HDGT CB5P) Replace Every 12 Months Filters may need to