Use these to calibrate one of the cheap yellow PH pens shown here. I used to buy a new Ph Pen every growth streak, but now I can just calibrate it and save money in the long run.
Accurate And Versatile Digital PH Meters For Food, Brewing, Hydroponics, Pools And More!
7 Review
80 Pieces Water Test Litmus Strips Litmus ph Paper Soil Acidity Meter Liquid pH Tester 1-14
10 Review
Digital PH Meter Tester - Tiaoyeer Water Quality Tester With ATC, 0.01PH High Accuracy, 0.00-14.00 Measurement Range, 0.01 Resolution For Drinking Water, Aquarium, Swimming Pools, Hydroponic
8 Review
Efficiently Test Your Antifreeze And Battery Acid With A 3-In-1 Refractometer
18 Review