Green-Tak SUS 304 Gravity Water Filtration is composed of high quality 304 stainless steel housing and washable PVDF gravity membrane. The washable gravity membrane is certified by NSF, FDA, SGS and even verified by SUPER LAB that can remove V. Cholerae up to 99.98%. The gravity water purification is the most cost-effective, durable and excellent performance water purification system for river water, rainwater and other ground water to purify for daily domestic water use and even potable water. Features Durable 304 Stainless Steel Filter Housing. No power consumption, environmentally friendly. High Flow Volume. No wastewater. Washable and Easy maintenance by residents. High Filtration Performance. Long Term membrane and filters lifetime.