We've run some analyses and crunched the numbers and it turns out that this Senku Ishigami 16 oz. Mug is the ideal vessel for achieving optimum caffeination. With a chalkboard-themed design featuring Senku crouching in front of everything you would need for a crash course in science from the Stone Age to modern days, it's perfect for fans of Dr. Stone! Hand wash only. Not dishwasher safe. Do not microwave.