pH Meter Calibration Powders As this is a powder, in a sealed packet there is no "shelf life". The contents will make up to 250ml each. Just add water or distilled water and solution can be used to calibrate your pH Meter or Handheld Pen Specifications: - 2x PH 4.01 - 2x PH 6.86 What's in the box 2 x PH 4.01 sachets & 2 x PH 6.86 sachets