NSF/ANSI 42 Certified Water Filter: certified for reducing aesthetic contaminants in drinking water, including chlorine taste and odor. For Berkey BB92 Black Filters: replacement filter cartridge designed to work with BB92 Black Filters. Berkey Gravity Water Filter System: compatible with the Berkey gravity filtration system. Fits Waterdrop King Tank Series, Purewell, and FSS Series: flexible compatibility with these tank series. Performance and compatibility: NSF/ANSI 42 certified; intended for use in gravity filtration setups with Berkey and compatible tanks. Use scenarios: At home: daily drinking water purification in a Berkey gravity system. Outdoors: camping, RV trips, or offgrid settings where electricity is not available. Emergency prep: backup filtration for power outages or water supply disruptions.