Designed for testing high concentration peroxide solutions (100 - 400ppm) It matches at 0, 100, 200, 400ppm Stiff, plastic strips offer durability Certificate of analysis available upon request Includes: (50) Strips High Level (HL) Peroxide strips test for residual peroxides in concentrations between 100 and 400ppm. They are primarily used for testing things like pools and hot tubes where peroxides, rather than chlorine, are used to sanitize . The strips are calibrated at 0, 100, 200, and 400ppm. These HL Peroxide test trips are suitable for semi-quantitative hydroperoxides and ether peroxides. Polymeric peroxides are not detected. Di-tert-butyl peroxide, dicumyl peroxide, or tert-butyl perbenzoate do not react (or will react with significantly reduced sensitivity).