This cartridge is for use with the WaterLink Spin Touch Photometer for pool and spa water analysis. The innovative WaterLink® Spin Touch® photometer does all your water testing for you. Each sealed SpinDisk® reagent cartridge contains the precise amount of reagent needed to run a complete series of tests. Now analysts can achieve test results without time consuming test and clean-up procedures. This ground-breaking analysis system is so simple anyone can use it! No vials to fill, no prep time, no guessing!