These test strips are the only strips IN THE WORLD with EPA approval for use in testing drinking water! They are easy to use, quick (40 seconds), non-toxic, non-hazardous, and greater than 90% accurate. There are no powder or liquid reagents to deal with and no measuring! These strips are so accurate they even come with a temperature compensation/ adjustment chart! Patented technology. If you are testing Free Chlorine any other way you are doing it the hard way!This product is ideal for testing drinking water, well water, wastewater, fill water for pool or aquarium, and any other water samples! They are easy to use and very accurate! SenSafeTM Free Chlorine Water Check (USEPA Approved)Detection Range: 0, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.2, 1.5, 2, 2.6, 4, 6 ppm (mg/L)Total Test Time: 40 SecondsNumber of Tests: Bottle of 50