All Oakton pH buffer solutions are freshness dated, and standardized against NIST-traceable references to ensure quality. ±0.01 pH at 25°C. Oakton pH Buffer Solution Bottles are labeled with the name and CAS number for all ingredients (for "Right-to-Know" requirements), and are supplied with an MSDS. Oakton Pouches are convenient, air-tight pouches with high-precision calibration standards. Ideal for field use- take them to your test site for on-the-spot calibration. Each box contains twenty 20mL pouches.