Docktails YETI Rambler 20oz - Seafoam Introducing the Docktails YETI Rambler mug in Navy. Coffee mug by day. Drink mug by night. The best part is that it's shatterproof, making it perfect for all your waterfront dining. YETI's Rambler 20 oz. is made from durable stainless steel with double-wall vacuum insulation to protect your hot or cold beverage at all costs. 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.