Be confident in your purchase we're an Authorized Coral RX Dealer. How cool is that?!?!? Features: pH 4.01 Calibration Buffer Solution - 20 mL (box of 25) Fundamental for the correct use of electrodes and for obtaining the most accurate and reproducible readings Sealed against light and air Ideal for on-the-spot calibration Simply open, insert the tester or electrode into the sachet and calibrate Formulated with a 5 year expiry Color coded for easy identification Specs: Accuracy Standard: 0.01 pH Value: 4.01 pH @25C Sachet Size: 20 mL Quantity: 1 Certificate of Analysis: No M10004B is a lab grade pH 4.01 buffer solution certified to meet the standard to an accuracy of 0.01 pH removing the inaccuracies involved with mixing calibration solutions from powder. Sachet packaging means that you get fresh solution every time. Ideal for infrequent or field use. No risk of using expired calibration solution. Milwaukee solutions are designed to help you achieve reliable and repeatable pH measurements while extending the life of your electrode.