Waterproof, dustproof housing that floats is certifiable to IP67 standards Replaceable sensor lets you reuse same meter body, saving you money. Hold function, Auto-Off Automatic Temperature Compensation Our waterproof microprocessor TDSTestrs and ECTestrs offer push-button calibration and �1% accuracy in a rugged waterproof housing. Never worry about losing your tester in a pond or tank; these testers float! Valox housing and stainless steel electrodes offer good chemical compatibility. Replaceable sensors let you reuse meter body without losing waterproof protection. Protective carrying case organizes meter and materials Includes everything you need for convenient calibration Calibration standards are made with NIST traceable materials Each kit contains TDS Singles calibration pouches (two each of 447 S, 1413 S, 2764 S, 15,000 S, and rinse water)and sample jar all in a hard shell carrying case with room for your TDSTestr (order Testr separately).TDS Singles are handy, single use pouches that each contain 20 ml of fresh calibration solution. Accuracy is 1% at 25C.