Any tumbler that's coming along for the ride needs to be tough enough to keep up. The Yeti Rambler 20 oz. is made from durable stainless steel with double-wall vacuum insulation to keep your coffee hot or iced tea cold at all costs. It's the Yeti tumbler your friends will envy. While the magnet on the included Rambler MagSlider Lid adds an additional barrier of protection for keeping drinks contained and preventing heat or cold from escaping, please note - this magnet component is not leakproof and will not prevent spills.