Wolfman wrote a review of Katadyn TRK Gravidyn Replacement Element on July 22, 2009
These gravidyns supply all clean potable water for two of us for extended stays at our cabin. I use a house filter first to get the chunks out, then the gravidyns. The time of year(muddy creek) dictates how often I have to clean the filters and that only takes a few minutes. I will buy these again.