APEC Ultimate high flow 5-stage complete filter set is made in USA with the highest quality filtration components to provide a longer lasting filter set to protect and prolong the lifespan of your Reverse osmosis system. Premium quality pre-filter cartridges lasts over 12 months while the membrane and post carbon filter last 3-5 years for fewer filter change outs and high performance impurity removal. Compatible for APEC RO-90, RO-PERM, and all other standard size under counter 50-90 GPD RO systems on the market. 1St stage: high-grade 10 inch high-capacity polypropylene sediment filter -removes dirt, particles, and rust. 100% pure polypropylene depth filter with exceptional dirt-holding capacity translates to longer life and fewer change-outs than existing string-wound or resin-bonded filters. 2nd and 3Rd stage: premium extruded carbon block 10 inch -gets rid of unpleasant chlorine, tastes, odors, cloudiness and colors. Also removes VOC and other common harmful agents from the water. Apec's extruded carbon block filters consist of activated carbon particles fused into a uniform block with enhanced adsorptive capacity and efficiency. Unlike granular activated carbon (GAC) filters, these extruded carbon block cartridges will not channel or bypass due to the extreme uniformity of their extruded activated carbon core. 4th stage: high rejection 90 GPD TFC reverse osmosis membrane. Removes a wide variety of impurities including arsenic, chlorine, lead, fluoride, chromium, radium and more. 5th stage: advanced coconut shell refining carbon 10 inch - TCR filter removes any possible residual taste from the tank. For over 20 years, apec has been an industry leading manufacturer of high performance ro systems.