Stainless Steel Travel Mugs feature double-wall vacuum insulation with a clear lid, surrounded by a removable silicone sleeve. The mug has a narrower bottom to fit most standard cup holders. It's 2X heat & cold resistant compared to a normal travel mug, and offers Sweat Free technology combined with Superior hot/cold retention. Mugs 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. The silicone material offers a unique design and feel while allowing you a good grip on your tumbler.