Extra pure RO-450 - Set of 3 replacement filters, Water System Parts Filters Replacement Cartridge ( Membrane ) Buy stage 2 in your system 96-99% reduction rate of bacteria, pesticides, herbicides, and heavy metals from tap water. extra pure ro-450 replacement filters has 3 filters including RO membrane that must be replaced periodically, The different filters represent the different stages that the water goes through while being purified, Generally - Pre-Filters and post-Filters in RO systems can last around 8 To 12 months between changes. RO membranes can last as long as 2 years extra pure ro-450 replacement filters uses sediment pre-filter to reduce sediment particles before the membrane filters out impurities larger than .001 microns. The GAC post filter treats for taste and odor. You can find and order all your filters at once high quality compatible with the GE Pro Elite RO-450 Water System Parts Filters Replacement . Stage 2 RO Membrane CTA 35-50 GPD - Replace Every 24 Months