Never watch a tester sink to the bottom of your tank or pond! The Oakton WD-35662-35 ECTestr 11+ is a multi-range waterproof tester that floats, so there’s no need to worry. Use the WD3566235 ECTestr 11+ for either cup-style or dip-style measurements. For cup style, pour a small amount of your sample directly into the sensor cup until it overflows; for dip style, simply immerse tester tip into sample. Replaceable sensor lets you reuse meter body many times over. Valox housing and stainless steel electrodes for good chemical compatibility. Note: Before measuring, calibrate tester as either cup style or dip style (depending on intended method of use).