Usage: This refractometer allows you to determine the ethylene glycol and propylene glycol concentration for frost protection in your car, solar installation, heat pumps, cooling systems, heating systems, or other machinery and water installations. Measurement Range: Ethanediol (ethylene glycol): 0 to -50°C; Propanediol (propylene glycol): 0 to -50°C; Windshield cleaning fluid - ethanol + water: 0°C to -40°C; Propylene glycol + water (SRF1): 0°C to -40°C; AdBlue: urea concentration 30% - 35%; Acid battery: 1.10 to 1.40 kg/L. Precision Measurement: Features an optical system with 4-8x magnification and stepless manual focus, suitable for all users. Designed to accommodate both nearsighted and farsighted vision; no need to wear glasses when reading measurements. Calibration: Perform zero calibration using distilled water at 20°C. Includes automatic temperature compensation. Note: Due to manual measurement and display variations, slight differences between individual units and photos may occur.