Hanna Instruments formulates this TDS calibration solution for use with their HI9813-6 meter. This solution allows for direct ppm calibration of total dissolved solids (TDS). Find the HI9813-6 HERE. Hanna designed this solution for premium quality. They prepare the 1,500 mg/L (ppm) TDS calibration solution against an NIST-traceable potassium chloride solution. Hanna prints the lot number and expiration date on the label of each bottle. They package it in an airtight container. They then apply a tamper-proof seal. This process ensures a high-quality solution. Hanna specially formulates their line of TDS calibration solutions. Each unopened bottle of solution has an expiration date of 5 years from the date of manufacture.