Any tumbler that's coming along for the ride needs to be tough enough to keep up. Our fan-favorite Rambler(R) 20 oz. Tumbler is made from durable stainless steel with double-wall vacuum insulation to protect the temp of your beverage at all costs. Like the entire Ramber(R) Drinkware Family, the 20 oz. Tumbler and MagSlider(TM) Lid are dishwasher-safe for easy cleaning. While the magnet on the included MagSlider(TM) 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.