Insulated: The inner mug has double steel walls that are vacuum insulated to retain temperature of beverages. Can keep your beverage hot or cold. You can choose to warm up the inside of the mug with hot water before pouring in your beverage. Outer Jacket: The steel mug has an outer plastic jacket with handle that doesn't let surface of mug get hot. Can be easily removed and cleaned. Dust Cover: The mug comes with a dust cover that has a silicone gasket. It will protect your beverage from dust or flies if you leave it unattended. Large Capacity: The Desk Mug easily fits in two small cups of beverage. That means fewer refills and fewer interruptions while you're working. Material and Capacity: The Desk Mug is made of steel and plastic and has a capacity of 400ml.