20 oz. Black Insulated Ringneck Tumbler features double-wall vacuum insulation with a slider lid. The mug has a narrower bottom to fit most standard cup holders. It is 2X heat & cold resistant compared to a normal tumbler. Our 20 oz Tumblers are made from 18/8 gauge stainless steel (18% chromium/8% nickel) - also known as Type 304 Food Grade.