Comparator system 2000, water test discs and reagent tablets A large selection o water test discs are available for colorimetric chemical analyses and colour cla sification. Each test disc is equipped with fade-free, non porous glass filters, he quality of which is not impaired by UV light or other environmental influence . Test discs whose code begins with ''N'', are designed for use in the Nessleris r 2150. Test discs which start with the letter ''C'' are designed for use in the essleriser 2250. All other test discs are designed for use in the comparator2000 . The most popular water test discs feature in the table below. Other testdiscs . The most popular water test discs feature in the table below. Other testdiscs