The Extech RF41 measures propylene/ethylene glycol freezing points from -50°C to 0°C. It also measures the specific gravity of battery acid from 1.11 to 1.30 and provides a quick reference of battery charge condition. Requires only 2 or 3 drops of solution for fast and accurate readings. The automatic temperature compensation provides repeatable measurements on an easy to read scale. Prism and lens come with a simple focus adjustment. Includes carrying case and calibration screwdriver.