The Perfect Mug to Keep Your Beverage Hot or Cold for Hours! 12 oz. double-wall powder coated stainless steel with faux cork base to protect surfaces from heat and scratches. Vacuum insulated with copper plating. Keeps drinks hot for up to 8 hours and cold for up to 12 hours. Clear plastic press-in lid and large rectangular handle. Wide 3.25" opening making it easy to fill with ice. Hand wash only for best results. Not microwave safe. Complies with Prop 65.