Harry Potter Muggle Worthy Heat Change Mug Experience a little magic with this Harry Potter Muggle Worthy Heat Change Mug. Simply pour in your coffee, tea or choice of hot beverage and watch as a beast appears through the keyhole. Features: Harry Potter novelty products Officially Licensed Design: Muggle Worthy Heat Change Mug Colour: Black Temperature sensitive design Reveals a beast through the keyhole when hot Materials: Ceramic Dimensions (approx. cm): 10 x 8 (H x Diameter)