The Hanna Instruments HI772-26 Seawater Alkalinity Reagent is a set of pre-measured reagents designed for use with the HI772 Marine Alkalinity Checker HC. This reagent kit provides 25 tests, allowing reef aquarists to accurately measure alkalinity (dKH) levels in their saltwater aquariums. Precise alkalinity testing helps maintain stable pH and supports coral growth and overall aquarium health.