A single-use 20 mL sachet of Milwaukee's lab-grade pH 4.01 buffer — the acidic reference point that pairs with a neutral 7.01 buffer for a precise two-point calibration. If you keep a planted tank and watch pH to dial in CO2, the 4.01 point matters: it anchors the lower, more acidic end of the scale where your readings actually live, so your meter stays accurate exactly where you need it. The sealed sachet protects the solution from air and light, giving you a fresh, uncontaminated reference every time, with no powders to mix and no open bottle drifting out of spec.
To use, tear open the sachet, dip in your rinsed probe, and run your meter's two-point calibration using both this 4.01 buffer and a 7.01 buffer. Works with any pH pen, meter, or controller, and is certified to ±0.01 pH.
Inventory Accuracy
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Pipersville, PA 18947
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