Uses positively charged electro-absorptive particles to attract and hold water contaminants like a sponge. Filter cartridge includes a patent-pending Upstream™ hygienic system to ensure each sip is a fresh one. Uses FDA compliant components and meets or exceeds NSF42 standards for reduction of chlorine. Not for use with hot water, tea, coffee, sweet or sour beverages. OKO takes the concept of the eco-friendly water container, NASA derived filtration technology, packaged in a smartly designed bottle with a high-tech blend of materials - ensuring that you're always drinking safe, pure, potable water in style. It's the ideal choice for everyday use, travelers, adventurers, and anyone who needs convenient access to clean, clear, crisp water. And with 3 sizes, 6 designer colors, and 2 levels of filters. OKO bottles are made from a customized blend of food grade plastics that has passed stringent SGS testing for FDA food contact safety. The bottle cap is made of Tritan, a BPA-free clear hard plastic that allows you to see the water filter working as you drink. O-ring carabineer to carry or hook the bottle onto a bag. And it's dishwasher safe. OKO's patent-pending filters use a positively charged electro-adsorption process to attract harmful agents and then kill bacteria on the filter surface using silver ions. The one-way Upstream Valve" allows for a steady. Fresh and clean-tasting water with every sip.