The Extra High Level Peroxide test strip is calibrated at 0, 500, 1000, 2500, and 5000ppm, and gives results in 90 seconds. These strips are used to test concentration levels of Peroxide solutions used in cases where strong disinfection is needed. This test strip is designed to work with solutions prepared from concentrated hydrogen peroxide only. It should not be used to test solutions made using “accelerated” hydrogen peroxide products. These type of solutions require specially formulated test strips.