This mug is loaded with top-to-bottom insulation to keep your coffee hot from the first pour to the last sip. And it's a space saver. When the lid is removed, the built-in grooves on the bottom help it nest perfectly with another just like it. Like the entire Rambler Drinkware Family, this stackable mug and included MagSlider Lid are dishwasher safe making them easy to clean. 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.