I bought these to check the peroxide levels in our hot tub which we sanitize with hydrogen peroxide rather than toxic chlorine. They work very well. I have a consistent reading between 50-100ppm which is very good. Just to make sure they work I tested one of them in a glass of tap water and it didn't discolor at all which showed me they give accurate readings. The price is also very fair.
Accurate And Versatile Digital PH Meters For Food, Brewing, Hydroponics, Pools And More!
7 Review
π PH 1-14 Extensive Storage Testing Monitoring: Optimize Your Storage with Precise pH Level Monitoring
6 Review
Efficiently Test Your Antifreeze And Battery Acid With A 3-In-1 Refractometer
18 Review
π― Honey Refractometer with Automatic Temperature Compensation (ATC) - Tiaoyeer Moisture, Brix, and Baume Refractometer for Honey, 58-90% Brix Scale Range - Honey Moisture Tester
31 Review