Buffer - pH 4.005, Concentration 4.005 pH, CAS Number 123-03-5, 7732-18-5, 877-24-7, Chemical Grade ACS, Chemical Family Type Solution, Calibration Certificate Yes, from an ISO Guide 34, Certified Reference Material Producer and an ISO 17025 A2LA accredited calibration laboratory and traceable to NIST, Shelf Life 12 mo, Standards ISO 17025, ISO 17034. This item has been restricted from sale in the following state (s): []