General Hydroponics 1500 PPM Calibration Solution, 1 Quart is no longer available

General Hydroponics® uses the highest quality reference solutions, 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 our solutions are precisely calibrated and yield reliable readings each time they are used.