The "Harry Potter - Heat Sensitive Morphing Mugs" are 11oz black mugs that reveal a hidden message when exposed to heat. Featuring a fantasy theme from the Harry Potter franchise, these collectible mugs are designed to change appearance as hot liquid is poured into them. With package dimensions of 4.41x4.29x4.29 inches and weighing 1lb, this heat sensitive mug is a unique and interactive item for fans of Harry Potter.