This portable 0-28% salinity refractometer is specially designed for salt water concentration detection, with measuring range 0-28% salinity, 0.1% resolution and ±0.2% measuring accuracy. Built-in ATC automatic temperature compensation eliminates reading deviation caused by temperature changes within 10-30℃. It adopts chrome-plated copper body with anti-slip rubber grip and corrosion-resistant stainless steel optical prism. Only a drop of water sample delivers instant data within 3 seconds, and adjustable eyepiece provides clear scale view. Equipped with calibration screw for easy zero calibration with distilled water, complete with storage case, dropper and cleaning cloth. Ideal for saltwater aquariums, seafood aquaculture, pickling brine and seawater lab testing. Battery-free optical structure for long service life, OEM customization of logo and package available, CE certified, lightweight for on-site salinity test in aqua shops, farms and hobbyists.