HHIP Synthetics Coolant Tester - Refractometer ~ Copper core for longer life. ~ Solution measuring range is 0-18%. ~ Accurately measures coolant concentration. ~ Optimize coolant use and tool life. ~ Just a few drops needed for test. ~ This refractometer is a simple instrument used for measuring concentrations of aqueous solutions. ~ The built-in Automatic Temperature Compensation (ATC) feature makes it get a consistently accurate reading, no need to control the temperature of the liquid deliberately. ~ Make sure it's at room temperature during use (0-25 ℃) ~ Includes instructions.