Replacement membrane element for the Microline Clack RO System T.F.C. - 4 or TFC 4 and Microline Reverse Osmosis System TFC 3. The Clack membrane replaces the TFC-335, TFC-435, T112-25 CLK and T112-25-CLK reverse osmosis membranes.TFC membranes are NOT Chlorine resistant and a carbon filter must be used prior to the membrane.