To verify the efficacy of McKesson OPA/28 Solution, user should test for the minimum effective concentration (MEC) prior to each use3 second dip time, read at 90 secondsLarge, easy-to-read indicator padDefinitive color identification comparison chart on each bottle18-month shelf life (unopened bottle), 6-month shelf life from date of opening --> Shop About Us Contact Us Reviews and Ratings McKesson OPA/28 OPA Concentration Indicator 50 Test Strips 50 Ct McKesson OPA/28 | MFG #73-OPA28B McKesson OPA/28 test strips provides a fast disinfectant reaction time and user-friendly color comparison chart. McKesson OPA/28 disinfectant helps ensure a safe and healthy environment for patients and staff. To verify the efficacy of McKesson OPA/28 Solution, user should test for the minimum effective concentration (MEC) prior to each use3 second dip time, read at 90 secondsLarge, easy-to-read indicator padDefinitive color identification comparison chart on each bottle18-month shelf life (unopened bottle), 6-month shelf life from date of opening Product Count: 1 Packaging Count: 50 Total Quantity: 50 Product Specifications McKesson Brand McKesson OPA/28 OPA Concentration Indicator