High Accuracy: These high-purity buffer powders ensure precise pH calibration with 0.01 pH accuracy at 25/77; They keep your pH testers sharp and reliable for consistent results. High Stability: These premium buffer powders maintain accurate pH values of 6.86, 4.00, and 9.18, even after long-term storage, saving you from repeated purchases for pH calibration. Individual Packets: Includes 6 packets of pH 4.00 solution powder, 6 packets of pH 6.86 solution powder, and 6 packets of pH 9.18 solution powder; Each packet is individually sealed to ensure freshness and accuracy, making them easy to carry and store. Quick Dissolution: These pre-measured pH buffer solution powders dissolve quickly, streamlining the calibration process; They contain no harmful substances, ensuring safe handling. Simple to Use: Compatible with any pH tester and probe; Just empty a packet into a clean glass beaker, add 250ml deionized or distilled water, stir gently until dissolved, and you're ready for calibration. Colour:As Shown Material:pH calibration powder Package Contents: 1set * ph down Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.