Hydrologic ARCS Stage 3 pH Neutralizing/Remineraliazing CarARCS Stage 3 pH Neutralizing Remineralizing Cartridge is designed to remineralize water coming from an RO unit. After adding it to your reverse osmosis system, you will get some mineral content added to the water, like calcite (calcium carbonate) and corosex (a magnesium compound). These minerals create good taste and health by neutralizing the pH of water. The water quality is close to the bottled mineral water. It serves as an excellent replacement