The Hydro Flask Standard Mouth Flex Cap is the ideal combination of strength and flexibility. Designed for ultimate portability, we crafted every detail with easy-carry comfort in mind and insulated it too, so you can go further, for longer, keeping your favorite beverage comfortably by your side. Compatible with all Standard Mouth Hydro Flask Water Bottles, the Hydro Flask lid features Honeycomb insulation to help keep cold drinks cold and hot drinks hot. Whether you're out in nature or stuck in the office, it's always a good idea to have an extra water bottle lid for your Hydro Flask. Maintain the temperature of your contents longer, so you can stay busy and get more done. An insulated water bottle cap to match your insulated water bottle. This Hydro Flask product is backed by a manufacturer's lifetime warranty.