Reverse Osmosis Filter Housing 2.5" x 10" (9-7/8”) filter housings are for point-of-use, not point-of-entry, meaning that they are best utilized for sinks or smaller points-of-use. These filter housings are what we use when we build our ProSeries RO systems. You can install these under a sink as a carbon pre-filter to remove chlorine, after an RO to add minerals to the water, and much more. The point-of-use RO filter housings are available in a number of configurations, including single, dual and triple applications. Inlet sizes vary from 1/4”, 3/8”, 1/2” and 3/4”.