Be confident in your purchase we're an Authorized Coral RX Dealer. How cool is that?!?!? Features: Ideal range for water conditioning (0 to 999 ppm). Units in ppm easily convertable to uS/cm. Factory calibrated with the ability to recalibrate if needed. Automatic Temperature Compensation (ATC). 300 hours continuous use (4 x 1.5V batteries included). Simple one point calibration. The Milwaukee CD97 Low Range Digital TDS Tester is designed for water conditioning, education and many other applications. The CD97 helps you make sure that your keep your filters up-to-date and clean for water filtration and is a cost effective tool for teacher's science labs. Keep PPM in your target range to help your achieve better results.