The Rambler 20 oz. Tumbler is crafted from durable 18/8 stainless steel with double-wall vacuum insulation to maintain your drink's temperature. The MagSlider Lid adds extra protection but isn't leakproof. It's dishwasher-safe for easy cleanup and fits in most cupholders. Puncture- and rust-resistant, this tumbler keeps drinks hot or cold until the last sip.