1-Year Compatible Filter Kit Rainsoft Ultrefiner UF50 Three Stage RO System Membrane Sold Seperatly 1-Year Replacement Filter Kit for RainSoft 21179 Reverse Osmosis System (RO Membrane Sold Separately) - 1- Year Replacement Filter Kit for Rainsoft Ultrefiner UF50 Three Stage RO System ( Membrane Sold Seperatly)