hydro flask 21 oz water bottle, sport cap - watermelon hydro flask the 21-ounce vacuum insulated hydro flask standard mouth insulated water bottle with sport cap is our most versatile medium-sized water bottle and one of our most popular. it is the perfect go-anywhere companion on your busiest days. stainless steel water bottle fits most ice cubes and is easy to drink from for hydration on the go. with a convenient 21 ounce capacity and a moderately sized opening, it's great for sports drinks, juice, smoothies or water. it stashes easily in a gym bag, a backpack side pocket or your car cup holder, and holds enough to keep you going for hours without weighing you down. this metal water bottle is as diverse as you! it is made from 18/8 food-grade stainless steel, and the tempshield double wall vacuum insulation provides top-notch insulation, keeping cold liquids icy cold for up to 24 hours and hot liquids steaming hot for up to 12 hours. the included standard mouth sport cap is bpa-free and phthalate-free and insulated to provide enhanced temperature protection. this sports water bottle is also compatible with our standard mouth flex cap. this hydro flask product is backed by a manufacturer's lifetime warranty.