Preheat ONE minute in the microwave. for coffee hot to the last sip, SAFE HANDLING PATENTED HotSmart mugs keep adding heat to your coffee (No other mugs in the world do that). In contrast to thermos or double wall mugs, HotSmarts have 3 sources of heat: a) The heat in the coffee itself which is NOT wasted heating up the mug b) The heat stored in the body of the mug c) The heat released slowly by the patented heater which stays STILL HOT after 30+ minutes (more than half hour). 1. Fine porcelain 11 FL OZ mug. . 2. This is not a regular mug; this is a PATENTED HotSmart® with a "Heater integrated.. Preheat the empty mug one minute -while coffee is brewing- fill it with HOT coffee. That's all you have to do. 3. Keeps coffee HOT for full enjoyment. It needs only one minute preheating in the microwave oven (maximum, DO NOT EXCEED) . 4. No wires, no batteries; you don't have to plug anything, 5. No risk of fire (Can be used at the office, shop, etc.); Heaters are normally forbidden by insurance companies.. 6. Green, no toxic materials used 7. Simply preheat the mug and now you are ready to ENJOY slowly your perfect cup of coffee or tea.. 8. SAFE HANDLING; the handle doesn't get hot. 9. The inventor (myself) has been using and testing the mugs for about 4 years before offering them for sale. A-Z GUARANTEE (As claimed or your money back).