Stainless Steel 30-ounce Tumblers feature double-wall vacuum insulation with a clear lid. It is 2X heat & cold resistant compared to a normal tumbler, and offers Sweat Free technology combined with Superior hot/cold retention. Tumblers are made from 18/8-gauge stainless steel (18% chromium/8% nickel), also known as Type 304 Food Grade. Hand Wash Only; Not Dishwasher Safe.