Hydration Thermos Hydro Flask Wide Mouth Thermo 710ml Green. The HYDRO FLASK Wide Mouth Thermo 710ml in Serpentine is the ultimate hydration solution for those on the go. With its sleek design and durable construction, this thermos is perfect for keeping your drinks at the perfect temperature all day long. The wide mouth design makes it easy to fill, pour, and clean, while the double-wall vacuum insulation ensures your beverages stay hot for up to 6 hours or cold for up to 24 hours. Whether you're hitting the trails or heading to the office, the HYDRO FLASK Wide Mouth Thermo is a must-have accessory for staying hydrated and refreshed throughout the day.