Morphing Mugs Harry Potter Book Cover Heat Reveal Ceramic Coffee Mug - 11 Ounces (The Order of the Phoenix) Color changing, heat-sensitive ceramic mug Heat-activation reveals hidden image Holds approximately 11 ounces Authentic Morphing Mugs and Officially licensed mug designed and printed in the USA by Trend Setters Ltd. While this mug may be used in the microwave, for the longest lasting, highest quality product, WE STRONGLY RECOMMEND AGAINST IT. HAND WASH RECOMMENDED