Black Berkey Purification Elements *The Black Berkey Purification Elements are made and assembled in the USA Black Berkey Purification Elements are the leader in gravity-fed water purification, backed by independent testing The Black Berkey Purification Element formulation has been tested by State and EPA accredited laboratories to exceed NSF/ANSI Standard 53 Includes: Two 9" Black Berkey Purification Elements with 2 washers, 2 wing nuts, and 1 priming button Installs in the upper chamber of any Berkey system. Elements can also be used to upgrade most other gravity-fed water filter systems Sold as a set of 2 elements Durability: Each Black Berkey Element is designed to purify approximately 3,000 gallons of water before needing replacement; 2 elements in a Berkey system will purify approximately 6,000 gallons of water before replacement is recommended Re-cleanable and self-sterilizing during the life of the element Elements come with a 2-year, pro-rated warranty