Complete rubbish, don't waste your money. I used them to calibrate my new brewing pH meter and spent two weeks trying to figure out why my pH levels were about 0.4 lower than my software predicted. I narrowed it down to my pH meter, so I recalibrated my meter with Milwaukee calibration solutions and then tested the pH of these buffers, 4.32 for pH 4, 7.22 for pH 7. Bullshit! So I kicked her out last night. . Listen to other reviewers who said it's far, buy something else!
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