Inaccurate. I can adjust my water to pH 5 and they will say "6.5". I can turn it to 8ph and they still say "6.5", they always say either 6.5 or it's a big jump to 9 or less. I compared it to a pen and drop. They don't work and that explains why I had so many deficiency issues with my last grow. Just use drops and make sure it's a yellow tennis ball and you're done.
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