The Low Level Chlorine test strip measures residual chlorine from 0-10ppm in increments of 0-0.5-1-3-5-10 in just seconds. This test strip detects residual levels of free chlorine. It is accurate within 5-10% of reading the color scale. Product DetailsManufacturer Part Number: CHL-10Manufacturer: Precision LaboratoriesUsage: For Measuring Chlorine Levels in Water