Ndur Portable Filtration Devices such as the 28 oz Flip Top Bottle are the most laboratory and field-tested of their kind in the world using EPA protocols and tested to NSF/ANSI Standards 42 and 53 by Broward Testing Laboratory. Each contains an Advanced Filter that uses the advanced technology of Seychelle. Advanced Filtered products remove what most other filters cannot; eliminating up to 99.9% of Micro-Organisms such as Giardia and Cryptosporidium, up to 99.99% of all chemicals and heavy metals, as well as up to 99.9999% of viruses and bacteria including E-Coli found in water sources. The 28oz Flip Top / Pull Top Bottles filter up to 100 gallons of water or more, depending on the quality of the source water.