Prism ION-Plated insulated 20 ounce Stainless Steel Polar Camel Tumblers features double-wall vacuum insulation with a clear slider 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.