Capacity: The flasks have a 3.2-liter capacity, suitable for holding a large volume of hot or cold beverages [5.2, 5.4].Design Features: They feature a sturdy plastic exterior, a glass inner lining for temperature retention, and a lid that doubles as a cup [5.2, 5.4].Temperature Retention: The vacuum insulation technology is designed to keep drinks hot or cold for extended periods [5.2, 5.10].