Omnipure's TQ56 series encapsulated membrane is compatible with both PuROTwist 4000 and PuROTwist 3000 Reverse Osmosis systems or any system that uses Omnipure Q-Series filters. It comes with a built-in flow restrictor and check valve and is easy to install.SpecificationsDimensions: 12.75" X 2.5"Replace every 24 monthsThin Film Membrane (TFM)