This is a Taylor Midget Comparator Copper Cuprione Test Kit. The K-1738 Kit tests for copper using the midget comparator and cuprizone chemistry. Copper in swimming pool water is common as there are many sources for copper to find its way into your pool water including chemical agents. Water naturally can hold a certain amount of dissolved copper also. You ideally do not want any copper or any other metals in your swimming pool water. Copper levels should be 0.2 ppm to 0.4 ppm. If it goes above 0.4 ppm, it is okay as long as it is under 1.0 ppm.