Balsamo 12 oz Ceramic Mug with Cork Base is made of ceramic construction with a natural cork base that is 85% cork & 15% polyurethane glue.. The tumbler has a matte exterior and glossy interior. The rubber seal lid has sliding drink opening and the natural cork bottom prevents furniture scratches and provides a non-skid base. The durable ceramic has a non-metallic taste, and will not rust or stain. Hand wash only. Do not put in microwave or freezer. Must be ordered in exact case quantities and may ship from CA. FDA certified.