Our chlorine test strips are a cost effective way to measure the concentration of free available chlorine in sanitizing solutions. The strips are simple to use and produce reliable results. Each strip measures concentrations between 10-200 ppm (parts per million), with color matches at 10, 50, 100 and 200 ppm. Each vial contains 100 strips and this pack includes 4 vials for a total of 400 strips.