Cello Monty Vacuum Insulated Double Walled Carry Flask for Travel, Home, Office, School (Coffee Mug). Cello Monty vaccum insulated Travel mug features double walled vaccum insulation with inner copper coating that retains the temperature, keeping beverages hot or cold for a prolonged period of time. This reusable double wall travel mug is made from 304 grade stainless steel both inside and out and is leak proof, durable, unbreakable, rust proof, odour free and 100% food grade. 450ml