Round Flask with Window- SALE! Beautiful window flask! 5 ounce round flask with mirror finish. Best with non-acidic liquids. Strong juices should not be put in this type of flask. Stainless Steel. Great for tailgators, or those folks who are hard to shop for! Best with non-acidic liquids. Strong juices should not be put in this type of flask. Click here to Contact Us Product Number: FL201