Unlike traditional camp mugs, this double-wall, vacuum-insulated body protects hands from hot or cold contents while keeping coffee, chili, or oatmeal nice and hot. And now, it stacks up and stores out of sight. Like all Rambler® Drinkware, the mug and lid are dishwasher safe. Please note: the mug's wide opening means content may cool quicker. That's why the mug comes with the MagSlider™™ Lid. Please note: do not place mug over external heat source or open flame. Vacuum seal or other damage may occur. This magnet slider is not leakproof and will not prevent spills.