Need a replacement lid for your 12 oz or 21 oz Hydro Flask? We have you covered. The Standard Mouth Loop Cap is a leak-proof, vented cap that allows hot vapors to escape while closing the lid, ensuring a smooth and easy seal. Perfect for everyday use, as well as the rigors of the outdoors, our caps aide in keeping your Hydro Flask contents hot or cold. The loop allows you to clip to a backpack or messenger bag and ensures your Hydro Flask stays with you wherever your adventure takes you. Our patent-pending loop caps are made from polypropylene PP#5 and are BPA-free and 100% recyclable.