Use For:This is a professional optical refractometer which is designed to measure the alcohol concentration of liquor. It is not suitable for measurements of the alcohol content in the beer or wine! Easy to Use:Place 2 - 3 drops of sample onto the prism, and then look through the eyepiece for both the density of alcohol readings. Convenient to Carry:This alcohol refractometer is lightweight and compact in size, it is very convenient to store and carry around. Measuring Range:Alcohol:0 to 80% v /v,with a sharp dividing line (blue-white) to ensure accurate readings. Tips:After use, it is strictly forbidden to wash directly into the water, wipe it with a clean soft cloth. For the optical surface, it should not be scratched or scratched.