General Hydroponics Calibration Solution is used to adjust your pH meter to 4.01. Easy to use, just dip your electrode into a small amount of the buffer and adjust the meter to read 4.01. Do not reuse solution. Suitable for all makes and models of pH pens and meters.
General Hydroponics reference solutions are of the highest quality, allowing growers to calibrate many popular brands of pH, EC and TDS meters (NaCl scale or the 442 scale). General Hydroponics technicians check each batch to ensure that these solutions are precisely calibrated and yield reliable readings every time they are used.
We recommend that you calibrate you pH meter regularly. The ideal pH range for most hydroponic crops is between 5.5 and 6.5.