Fuel Gauge Coffee Mug is a fun way to see your mug's temperature and capacity just by looking at the colour. Red means hot and black means empty! This unique mug features a fuel gauge graphic that gradually turns red as you fill it with a hot beverage, showing when it's "full." As you sip, the red gauge slowly drops, turning black to indicate the remaining level of your drink. Perfect for coffee lovers who want a playful reminder when it's time for a refill, this mug adds a touch of fun to any morning routine and makes a great gift for anyone who enjoys a hot cup of coffee.