Check the listing for details. Vertex PWC-3500 Replacement Filter Kit (Without RO Membrane). Condition: New. Listed at 60.97 USD. Filter Replacement Kit for Vertex PWC-3500 Reverse Osmosis System (RO Membrane Sold Separately) INCLUDES: * STAGE 1 - 1x Sediment Pre-Filter (K5605-JJ) - Replace every 6-12 months or as needed * STAGE 2 - 1x Carbon GAC Pre-Filter (K5633-JJ) - Replace every 6-12 months or as needed * STAGE 3* - 1x (RO Encapsulated Membrane MH-4206 Sold Separately or with Replacement Kit YSM-VERPWC3R) - Replace every 24 months * STAGE 4* - 1x Carbon GAC inline Post-Filter (K2533-JJ) - Required only for PWC-3500R or system - Replace every 6-12 months or as needed *This stage only included in the 4-Stage PWC-3500R systems Filters may need to be replaced more often than indicated depending on water contaminant levels and volume of water being treated.