Apera Instruments pH Calibration Buffer Solution Kit (pH 4.00, 7.00 & 10.01, 8 oz. each), plus 4 oz. 3M KCL Soaking Storage Solution. Apera pH calibration buffers are produced in an ISO 9001:2015 facility with ISO 17025:2017 accreditation using high-purity reagents, deionized water and certified analytical balances in a temperature controlled environment. Reported values are accurate to +/- 0.01 pH at 25°C and are traceable to NIST Standard Reference Materials (SRMs). MSDS documents are downloadable. Certificate of analysis can be achieved by request. All pH buffers have a 2-year expiration from manufacture for an unopened bottle.