Hydrotech Reverse Osmosis Membranes are available in both thin film composite (TFC) and cellulose triacetate (CTA) materials, and with permeate flow rates up to 75 gallons per day. Since all of these membranes are the same physical size, it is important to identify which membrane your RO system requires. The easiest way to do this is by identifying the color of the tape wrapped around your membrane. TFC membranes will have a yellow or green wrap, along with the colored tape to identify the permeate flow rate. CTA membranes will have a blue wrap, along with the colored tape.