The Ettore Aquaclean 21 in. RO Membrane is a replacement ro membrane for the Ettore Aquaclean Pure Water Cart by RHG. All of the Ettore Aquaclean Pure Water Systems feature the RHG cartridges and 'quick disconnect' system. These are some of the easiest systems to maintain on the market today. Simply disconnect 2 fittings to remove the cartridge and reconnect them to the new one. Its that easy. No more wrenches to open filter housings or trying to shove that white ring back in.