OKO's advanced filtration water bottles are made from a customized blend of plastics that have passed stringent SGS testing for FDA food contact safety. The bottle cap is made of Tritan, a BPA-free clear hard plastic renowned for its durability and clarity that allows the user to see water filtration in action as you drink. The bottle's body is made of an ultra-light polypropylene material used popularly in food storage containers worldwide. Our semi-soft nozzle and washer create functional accents and the contoured shape makes the bottle easy to grip. The O-ring carabineer is used to carry or hook the bottle onto a bag. OKO Level-2 filtration, originally developed through a NASA grant for space stations, is now available for consumer use. Simply put, it is the state-of-the-art in water filtration technology. The filter produces superiorly-efficient filtration with a powerful flow. Our patent-pending Upstream Valve returns any backwashed fluid into the "unfiltered" water area for re-filtration and to ensure that every sip is pure, fresh and clean. OKO bottles are dishwasher safe and easy to clean. See manual for care instructions.