Batman likes the dark. He can see in it. You can't. And that's not good if you're thirsty and the lights are off! The Batman Glow in the Dark Mug fixes that problem with a slick glow-in-the-dark Batman Logo. Black glazed stoneware construction holds 10 ounces of your favorite Bat-beverage. Handwash. Not dishwasher or microwave safe.