Milwaukee OPR Solution 200-275 mV (MA9020) is a lab grade ORP 200-275 mV solution certified to meet the range. Milwaukee OPR Solution 200-275 mV is used to check the health and acuracy of an ORP electrode. Milwaukee solutions are designed to help you achieve reliable and repeatable ORP measurements.Milwaukee OPR Solution 200-275 mV+ fundamental for the correct use of ORP electrodes and for obtaining the most accurate and reproducible readings+ sealed against light with air tight, tamper proof cap+ ideal for fast accuracy check+ simply open bottle, pour small amount into a beaker or container and insert the tester or electrode to start the ORP mV check process