With its rugged design and build the TDS-3 is an ideal meter (tool) that can be used for any application; water purification, to hydroponics, to industrial waste water treatment. Come with a black vinyl carrying case. Features: Hold Function, Auto-off Function (After 10 minutes), Built-in Digital Thermometer, Includes Carrying Case with Belt Clip, Factory Calibrated with a 342ppm NaCl solution. Meter can be re-calibrated with a mini-screwdriver.