Brondell H2O+ Circle RO Membrane Replacement Filter Replaceable RO membrane filter for the Brondell Circle reverse Osmosis system Extended RO Membrane life  automatic filter flushing significantly extends the life of the RO membrane to 2 years Quick change filters - twist and seal filters make filter replacement a breeze Gold Seal certified by WQA (Water Quality Association) for trusted performance Replacement filter RF-40 RO Membrane