M10007B is a lab grade pH 7.01 calibration solution certified to meet the standard w/an accuracy of +/-0.01 pH removing the inaccuracies involved w/mixing solutions from powder. Sachet packaging means that you get fresh solution every time. Ideal for infrequent or field use. No risk of using an expired calibration solution. Milwaukee solutions are designed to help you achieve reliable & repeatable pH measurements while extending the life of your electrode.