Royalford 4L Stainless Steel Airpot Insulated Vacuum Thermal Flask Jug The Royalford 4 Liter Airpot is the ideal solution for easily serving larger volumes of hot and cold drinks. The double wall design helps to reflect internal heat so your hot drinks can stay hot for long hours. If you prefer chilled squash or juices the insulation prevents any ambient external heat from warming your drink too far. The stylish stainless steel finish on the outside is reflected in the flask’s internal construction. By using steel instead of glass the flask is more robust and there is less risk of breakages.