This our replacement filter set for our ProSeries 6 stage Remineralizer system.  This set works with standard reverse osmosis systems. Most reverse osmosis filter sets should be changed once per year.  Depending on your water quality, filters generally get dirty and should be replaced in order to keep your membrane working properly, and keep cleaning contaminants out of your drinking water.  The membrane is not included in this set but it is offered as an additional option, select the membrane option and it will be added to your order.  It's recommended because you should change membrane every 3 years or sooner if your water quality is poor. We also have a sanitizer kit available as an add-on option.  When you change your filters it's recommended that you sanitize your systems before replacing them, to help keep the system clean from harmful contaminants. Filter set includes: This set includes: (1) 5 Micron Sediment Cartridge Filter(2) 5 Micron Carbon Block Cartridge Filter(1)  (1) 1/4" Female Inline Alkaline Remineralizer Filter(1) 10" Inline GAC Cartridge Filter (1/4" Female with 2-3/8" fittings and 2-1/4" Fittings) Membrane is not included in this set, you change membrane every 3 years