30 oz. Tumblers from Cold Jack are made from 18/8 Kitchen Grade Stainless Steel. They are double-walled and vacuum insulated so they keep your drinks cold (or hot) all day, and will not sweat (so no need for coasters or napkins). The airtight clear sliding lid makes it spill proof as well, so it is perfect for bumpy car or boat rides! For a limited time, we will customize your tumbler free of charge ($10 regular charge) and because we laser engrave our products, they will never fade or scratch off!!