You simply press the button on the lid and the UV light will purify your water in less than 15 mins. Interior remains free from contamination. UV light and battery are incorporated in the lid, and USB battery can have a charged life up to two weeks. Stainless steel, double walled, vacuum insulated bottle that you can fill and drink purified water any-where. Great for camping, travel and outdoor use. Hot up to 12hrs. and cold up to 24 hrs.