Complete set of Replacement water filters for your under sink RO Pure (WP531411, WP531407) or Zero/Pure Plus (WP531517, WP531417) Sediment Filter Pre- Filter Activated Carbon Pre- Filter 50 GPD TFC Membrane Element Filter Activated Carbon Post- Filter Attention: This filtration kit will NOT fit the Kwik-Change Reverse Osmosis System Fully replacement for Premier 4 Stage Pure Plus/Zero Pure Plus Reverse Osmosis System, Include Sediment Filter, Pre & Post Carbon Filter and RO membrane Element, please see below details: Stage (1): 5-Micron Sediment Filter Made of Pure Polypropylene . Compatible with WP105311; Stage (2) Activated Carbon Post- Filter. Composed of High Performance Coconut carbon, Compatible with WP105351; Stage (3): 50 GPD TFC RO Membrane filter. Compatible with WP105331; Stage (4) Activated Carbon Post- Filter. This Filter provides a Finer Conditioning of the Pure Water. Compatible with WP105341. Fits your under sink RO Pure (WP531411, WP531407) or Zero/Pure Plus (WP531517, WP531417)