PINPOINT High-Precision +400mV ORP/REDOX Calibration Fluids Kit, 10 piece set. With a precise measurement of +400mV, the occasional retesting with this fluid will keep your readings dead-on accurate. Also very useful to determine if an ORP/REDOX probe is ready for replacement. Solution is highly accurate for a maximum of 60 to 90 minutes after exposure to air. This set contains 10 pouches. Each pouch is totally sealed from air and light. They are ready to use, no mixing required and are field portable. Each pouch contains ample fluid for calibration (approx. 25 mL). Do not reuse solution. Do not store ORP/REDOX probe in this calibration fluid. Questions? Just contact us.