SeltzaRO sits under your sink and can be installed individually or inline with SeltzaHub to deliver filtered water. For advanced filtration the SeltzaRO comes included with the following filter cartridges: Stage 1 - PCB (Polypropylene Carbon Block) - Removes sediment, rust, chlorine, organic contaminants and other particle impurities in water. Replacement: 6-12 months. Stage 2 - RO (Reverse Osmosis) - Filters out harmful substances such as heavy metals, inorganic salts and chemical residues in water. Replacement: 24-36 months. Stage 3 - CB+MNR (Carbon Block + Remineralization) - Offers dual function. First it remove impurities, odors and bad tastes in water. Next it provides alkaline correction and mineral infusion. Replacement: 6-12 months. Benefits of Remineralization: Gently restores essential minerals to enhance the taste and health benefits of purified water. Minerals include calcium, magnesium, sodium and potassium. Helps achieve a balanced, natural-tasting and gently alkaline drinking experience. Replacement filter cartridges can be purchased as needed. USER GUIDE & INSTALLATION