HM Digital TDS-EZ Water Quality TDS Tester, 0-9990 ppm Measurement Range , 1 ppm Resolution, +/- 3% Readout Accuracy by HM Digital (209) Buy new: $25.95 $15.50 36 used & new from $13.50 (Visit the Best Sellers in Power & Hand Tools list for authoritative information on this product’s current rank.)

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#6: HM Digital TDS-EZ Water Quality TDS Tester, 0-9990 ppm Measurement Range , 1 ppm Resolution, +/- 3% Readout Accuracy