Replacement Probe for Hanna HI9813-6N Waterproof pH/EC/TDS Meter Light Controllers They are required for the

They are required for the calibration of pH meters

simply re-wet by placing them in a bowl of lukewarm water

The PC diaphragm evens that out so every dripper meters the same 0

Large Water Passages: Minimizes blockages for consistent flow

Replacement Probe for Hanna HI9813-6N Waterproof pH/EC/TDS Meter Light Controllers They are required for theHI 9813 6N is a versatile, water resistant multiparameter portable meter specifically designed for agricultural applications such as hydroponics, greenhouses, farming and nurseries. It features an extra large LCD that clearly displays the parameter being measured as well as calibration instructions. Calibration is fast and easy with knobs located on the front panel of the instrument. HI 9813 6N is designed for simplicity of use in taking pH, mS cm,