These sachets are for use with the Hanna HI9813-6 GroChek portable pH/TDS/EC/Temp meter, which utilizes the Cal Check Solution to determine whether the probe is in need of cleaning or replacement.
The sachets should only be used once, then discarded, in order to avoid contamination and improper readings.
Item Number: 134389
Manufacturer: Hanna Instruments
Manufacturer's Part Number: HI 50021
Brand: Hanna Instruments