The Yeti Rambler 20-oz. is made from durable stainless steel with double-wall vacuum insulation to protect your hot or cold beverage at all costs. This 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 leakproof and will not prevent spills.