The Merlin Garden Pro Reverse Osmosis Membrane (HydroLogic 22085) filters a wide range of harmful contaminants from your water. Reverse osmosis is the premium standard in filtration for removing dangerous chemicals prior to watering your garden plants. The HydroLogic Reverse osmosis membrane element fits the Merlin Garden Pro Water Filter System. Reduces contaminant parts per million (PPM) by greater than 95%. Helps reduce low levels of iron and sulfur. Simple maintenance plan: Replace the cartridge about every two years.