HI7021L is a quality ORP test solution made from reagent grade chemicals and used to test platinum and gold ORP electrodes. Hanna test solutions have the lot number and expiration date clearly marked on the label and are air tight with a tamper-proof seal to ensure the quality of the solution.Prepared with reagent grade chemicalsAllows for a quick check of your ORP electrodeAir-tight seal to ensure the quality of the solution