The Rambler 30 oz. Tumbler is made of 18/8 kitchen-grade stainless steel, has double-wall vacuum insulation, and No Sweat™ Design. Double-wall vacuum insulation keeps cold drinks cold and hot drinks hot. Now that the Rambler family is sporting DuraCoat Color, it's pretty good looking to boot, making it a perfect stainless steel drinking vessel. It won't fade, peel, or crack through extended field use, and the DuraCoat Color provides additional grip to the Rambler's exterior.