Refractometer technology is based on the principle of refractive index of different liquid concentrations, which is an optical instrument with high accuracy and portability. calibration screw: drop distilled water on the prism, twist the zero adjustment screw, so that the dividing line is adjusted to the scale 0%. Adjustable eyepiece: When the scale in the territory is not clear, you can gently rotate the eyepiece to adjust it. anti- and anti-rust, bright as new, beautiful atmosphere. Anti-slip rubber cover feel soft, rotate lightly, not easy to slip off. Clear reading, fast detection, accurate measurement, easy to use. suitable for canned food, juice manufacturing, brewing and fermentation, beverage, fruit, honey harvesting and other fields. test range 0-90%, measurement accuracy: 0.1%. With temperature compensation function, to overcome the deviation of data caused by temperature changes, making the data more accurate. Item Type: Refractometer Model: RHB-90ATC Sugar Test Range 0-90% Measurement Accuracy: 0.1% Automatic Temperature Compensation (ATC): 10~30 (50~86) Package List: 1 x Refractometer 1 x Dropper 1 x Screwdriver 1 x Cloth(random colors, don't accept the specified color) Colour:As Shown Material:Metal Package Contents: 1 set x tester Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.