Oakton WD-35634-35 PCTSTestr 50 pH/Cond/TDS/Salinity Pocket Tester, Waterproof, -1 to 15 pH, 0 uS to 20 mS, 0 ppm to 10 ppt TDS, 0 to 10 ppt Salinity. The tester can even stand upright when the cap is used as the stabilizing base.
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