GroLine pH/Temperature Probe (HI981412-00)HI981412 00 is supplied with HI10063 pH temperature probe, 4. 01 pH buffer solution, 20 mL (3), 7. 01 pH buffer solution, 20 mL (3), power connection cable, instruction manual and quality certificates for instrument and probe. Maintaining the correct pH of plant soil or hydroponic nutrient solution is an ongoing task. Macro and micro nutrients, as well as calcium and magnesium bloom boosters, require the correct pH for absorption into the plants root