This 4-piece portable optical concentration refractometer set includes four independent testers for Brix sugar, salinity, alcohol and antifreeze liquid. All units are equipped with ATC automatic temperature compensation to eliminate reading errors caused by temperature changes. Constructed with chrome-plated copper body and anti-slip rubber grip, the corrosion-resistant optical prism delivers instant accurate results with just one drop of liquid. Adjustable eyepiece offers clear scale reading, and calibration screw allows easy zero calibration with distilled water. Full accessories including storage case, dropper and cleaning cloth are included. It covers testing scenarios of fruit drinks, aquaculture, wine brewing and auto cooling systems. OEM customization for logo and package is available, CE certified, lightweight and sturdy for on-site concentration detection in shops, orchards, auto repair shops and breweries.