Milwaukee Instruments, C65, Low Range Waterproof Conductivity Pen with ATC and Replaceable ElectrodeC65 Includes Only:C65 Conductivity PenBattery 3 x 1.5VThe Milwaukee C65 Conductivity Pen is designed for aquariums, aquaculture, agriculture and pools to help you make sure that your fish or plants are receiving the right amount of nutrient to help keep your water clean and clear. Keep EC in your target range to help your achieve better results.Features: Measures conductivity and temperature with automatic temperature compensation.Ideal range for Aquaculture (0 to 1999 uS/cm).Units directly in uS/cm (no conversions required). Factory calibrated with the ability to recalibrate if needed.Replaceable electrode.Fully waterproof to IP65.250 hours continuous use (3 x 1.5V batteries included).