The Peroxide test strip measures residuals from 0-100 ppm in increments of 0-0.5-1-3-5-10 in just seconds. This test strip detects residual levels peroxide. It is accurate within 5-10% of reading the color scale. Product DetailsManufacturer Part Number: PER-100-1V-50Manufacturer: Precision LaboratoriesUsage: For Measuring Chlorine Levels in Water