Genesis Water Technologies GW-CSB1 Replacement Fine Sediment and Carbon Block Pre-Filter for The GW-MFS-M or GW-MFS-NM Filtration Unit Two stage carbon block and sediment pre filter cartridge Sediment filter removes finer particles protecting the nano carbon filter stage Activated carbon block filter removes water contaminents One cartridge provides the second and third filtration stages for the GWT system Proudly Made in America