The fan-favorite Rambler 20oz. Tumbler is made from durable stainless steel with double-wall vacuum insulation to protect the temp of your beverage at all costs. The 20oz. Tumbler and MagSlider Lid are dishwasher-safe for easy cleaning. The magnet on the included MagSlide Lid adds an additional barrier of protection for keeping drinks contained and preventing heat or cold from escaping.