Cynthia Magical ON/OFF Switch Color Changing Mug-Black Tea Coffee Mug GREAT VALUE - Come with different Mugs,great gift idea especially with the holidays for everybody. HOW TO ACTIVATE COLOR CHANGE - In order to activate cup the temperature of the hot liquid should be over 70C/158F5. At that temperature it is possible for the color of the mug to change. KEEPS TRACK OF COFFEE TEMPERATURE - Dont you hate it when you take a sip of your morning coffee and its cold? Well with this cup you dont have to go through this unpleasant experience anymore. As your coffee cools off, your mug turns back to pattern of change before! 100% CUSTOMER SATISFACTION GUARANTEED - Cynthia guarantees that you will always be satisfied with your purchase from us. We only use the best materials for our products and are always available to aid our customers. WARNING - Do not put them in the microwave and do not wash by dishwasher.