Hi all, We updated the reagent product code used for the HI772 dKH Alkalinity Checker. The new code is: HI772-26 Marine Alkalinity Checker® HC Reagents for HI772 (25 Tests) http://hannainst.com/marine-alkalinity-checkerr-hc-reagents-25-tests.html This have been updated from the HI755-26. The chemical used is still the same we just created a new code to match our reagent categorization system. The HI755-26 Alkalinity reagent for the ppm Marine Checker is still an active code and the reagents can be used interchangeably. Thank you for testing with Hanna Instruments!