General Hydroponics pH 4.01 Calibration Solution, 1-Quart
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<b>[Product Information]</b><br>
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<li>Highest quality reference solutions</li>
<li>Compatible with many popular brands of PH, EC and TDS meters (NaCl scale or the 442 scale)</li>
<li>Each batch is checked to ensure that our solutions are precisely calibrated</li>
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