Watts Premier Reverse Osmosis Membranes utilise an internal cheque valve, so make sure to use only Watts Premier replacement RO Membranes (yellow outer wrapping tape colour) for your RO Systems.Watts Premier engineers are constantly working to provide a superior long lasting quality product to you our customers.Since Premier has RO Systems out in the marketplace since 1988, we noticed that cheque valves, typically placed in the elbow of the system, have a tendency to wear out over time.A RO system with a faulty cheque valve will become less efficient by running constantly.By placing the cheque valve in to the membrane, you are assured constant efficient performance due to the periodic replacement of this critical component of the RO system.Using Filmed sheeting, the Watts Premier Membranes are compatible with Premier as well as all standard reverse osmosis systems.This semi permeable membrane effectively reduces TDS and sodium as well as a wide range of contaminants such as Arsenic, Lead, Percolate, Chromium, Copper, Radium and Protozoan Cysts, such as Giardia and Cryptosporidium.The heart of your Reverse Osmosis system reduces impurities down to 1/10,000 of a micron.Fits 5SV, 4SV, Manifold and Zero Waste systems.