Deionized Water is free of minerals, ions, volatile organics, and other impurities—higher purity than distilled water. Filtered by Reverse Osmosis, UV Sterilization, and Quad-cartridge filtered. Resistivity 1-15 MO/cm No mineral buildup in car radiator, steam iron, etc. No spotting glass or glassware. Clean sensitive instruments and devices. Helps keep fishtanks cleaner. Water sensitive plants. Packed in four heavy-duty 1 gallon jugs with handle, resealable cap, and quality-assurance seal. Easy storage and easy pouring. 4 gallons as a CASE.