20 oz. Stainless Steel Polar Camel Tumblers features double-wall vacuum insulation with a clear lid. The mug has a narrower bottom to fit most standard cup holders. It is 2X heat & cold resistant compared to a normal tumblers. Polar Camels are made from 18/8 gauge stainless steel (18% chromium/8% nickel) – also known as Type 304 Food Grade. Not recommended for dishwashers, hand wash only.