3 seeds + 1 free seed
5 seeds + 2 free seeds
About 20 ml of solution for calibrating pH meters.
Meters that are used with a calibration point of 4.01, or in those using a two-point calibration system.
Using it is as simple as opening the envelope and placing the meter on it then waiting a few minutes. Following this, you need to adjust the meter to the value indicated on the envelope.
We recommend calibrating the meter regularly to be sure of obtaining reliable values.