The 21 oz vacuum insulated Hydro Flask is our most versatile medium-sized water bottle and one of our most popular. With a convenient 21 oz capacity and a moderately wide mouth opening, it's great for sports drinks, juice, smoothies or water. It fits nearly any size ice cube and is easy to drink from on the go. This flask as diverse as you! The 21 oz insulated Hydro Flask is made from 18/8 food-grade stainless steel, and the double wall vacuum insulation provides top notch insulation power, keeping cold liquids icy cold for up to 24 hours and hot liquids steaming hot for up to 6 hours. Hydro Flask is proud that all our products are BPA-free, recyclable and backed by a lifetime warranty. Look for the H-guy and Hydro Flask logo to ensure you're getting the market's premium insulating beverage bottle.