The 3MROP411-20A 3M Under Sink Reverse Osmosis Replacement Water Filter Cartridge is a pre-filter sediment cartridge which can reduce levels of chlorine taste and odor, lead, and particulates. This filter features a slim profile design that allows for minimal space requirements and allows for more space beneath your sink. Easy operation and installation mean that replacing this filter and maintaining your system is a breeze. Quick change cartridge design means no hassle with tools and other appliances. The 3MROP411 is a replacement cartridge for the 3MRO401 reverse osmosis system.