Mantis Digital Refractometer is ideal for measuring aquarium water salinity, either directly or via its included saucepan, plus an ideal storage case. Key features of the digital refractometer: High resolution in the values High measurement accuracy (0.0001%) Large, clear and backlit LCD display Low battery warning sound Warning sound start and end of measurement Temperature counter Temperature reading of the sample Water resistant Battery included Undoubtedly, an indispensable tool for all those who love to control aquarium values.