Genuine Hydro Flask custom parts! Small Flex Boot Color: Black For 12-24oz bottles. *Please note: Does NOT fit 32oz bottles.* Attaching it to the bottom of your bottle protects it from dents, scratches, and dirt if dropped. You can also express your individuality by matching it with your favorite colors. It's also fun to look forward to new colors every year! It's also fun that you can't get the old colors when new ones come out!