PINPOINT High-Precision pH Calibration Fluids Kit contains 10 packets: 5 pouches of 4.000 +/- 0.002, 5 pouches of 7.000 +/- 0.002 Calibration Fluids. Each one comes in it's own plastic-lined, foil envelope packet. They are ready to use, no mixing required, are extremely accurate and field portable. Each packet contains ample pre-mixed fluid for calibration (approx. 25 mL). Referenced to NIST standard materials.