Hydro Flask"s insulated water bottles are made of high quality food grade 18/8 stainless steel. The bottles have no liner (like most aluminum bottles) and are BPA free. Unlike plastic water bottles or single wall stainless bottles, Hydro Flask will keep your beverage of choice at your preferred temperature for hours, whether you choose hot, cold or room temperature liquids. All Hydro Flask products feature a lifetime warranty and are double wall vacuum insulated. They are designed to be lightweight, making them great for long hikes, days on the beach, hot yoga classes, golf, long road trips or everyday office use. Even when filled with ice, the exterior of your Hydro Flask will never leave a puddle on your desk, drip on your shirt, or sweat in your bag.