The Pentair TLC-50 (555583-43) is a thin layer composite (TLC) reverse osmosis (RO) membrane. The TLC-50 is a replacement part used in many residential and small commercial reverse osmosis systems. It has nominal output of 50 gallons per day and is a "dry packed" membrane to maximize shelf life. It has high purification effectiveness even with very high input TDS. This membrane is used in NSF Certified Pentair RO systems.