The Purist Hydroflo WaterGate Bottle features an amorphous silicon dioxide coating thats infused into the inner-wall of the bottle. Essentially, this forms a glass-like finish that provides a totally natural, and completely inert, solution to the problem of your drinks staining the bottle or leaving behind any residual aftertaste. This infusion also shields your fresh water from tasting like plastic on very hot days, making it akin to drinking straight from a sparkling clean glass.