Any tumbler that's coming along for the ride needs to be tough enough to keep up. Our Rambler® 20 oz is made from durable stainless steel with double wall vacuum insulation to protect your hot or cold beverage at all costs. Like the entire Rambler® family, the 20 oz tumbler and its lid are dishwasher-safe for easy cleaning. While the magnet on the included 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 leak-proof and will not prevent spills.