GroLine 1413 µS cm Conductivity Standard with Certificate (230mL Bottle) combo meter calibration Made in USA: Filters manufactured homebrew equipment Made in USA: Filters manufactured and tested to the highest standards Compatible Meter: Milwaukee Mi106 pH ORP Temp Meter 413 µS cm conductivity solution standardized with a conductivity meter that has been calibrated with potassium chloride NIST 2202 SRM (Standard Reference Material) in deionized water for analytical use in accordance with ISO 3696 BS3978 Hanna conductivity solutions have the lot number and expiration date clearly marked on the label and are air tight with a tamper proof seal to ensure the quality of the solution