30 oz. Stainless Steel Polar Camel Tumblers feature 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 tumbler. Polar Camels are made from 18/8 guage stainless steel (18% chromium/8% nickel) – also known as Type 304 Food Grade. This item is not dishwasher or microwave safe.