Perfect for functional use, the Hydro Flask® 21 oz. Standard Mouth Bottle with Flex Cap makes the perfect hydration companion. The double wall vacuum insulation keeps your hot beverages hot for up to 12 hours, and your cold drinks cold for up to 24 hours. Made from durable food-grade stainless steel with a powder-coated finish, the 21 oz. bottle features sweat-free construction for easy grip in any conditions.