The F15-75 2-year filter pack comes with a total of 15 replacement filters so the filters can be changed on schedule for 2 years. 4x 5 Micron 10" Sediment Filters (1st Stage, #FP15): Removes dirt, rust, sand, and other particles. Replace approximately every 6 months. 4x 5 Micron 10" Granular Activated Carbon (GAC) Filters (2nd Stage, #FG15): Absorbs chlorine, halide, organic contaminants, odors, and other impurities that contribute to bad tastes and odors. Replace approximately every 6 months. 4x 5 Micron 10" CTO Carbon Block Filters (3rd Stage, #FC15): Further removes any remaining chlorine, tastes, and odors. Replace approximately every 6 months. 1x High Rejection . 0001 Micron TFC Reverse Osmosis Membrane (4th Stage, #MC7): The heart of the RO system. Produces drinking water at a rate of 75 gallons per day. Replace approximately every 2-3 years. 2x Post Carbon Inline Filters (5th Stage, #FT15): Polishes the water from the tank before it is delivered to the faucet. Replace approximately every 12 months. This filter pack fits the iSpring RCC7, RCC7P, and most other RO systems that use standard sized filter housings including Flowmatic, PuROLine, Crystal Quest, and Apec.