These was the most perfect holiday gift we ever given to every family member and friends the year it first arrive the store. I've received great videos they took, shows how fun to actually watch how your coffee is being mixed inside that cup!
It is made of glass, it is dishwasher safe. Although it is durable, it needs TLC with caution to leave spaces in between inside the dishwasher, avoiding bumping to each other and prevent from breaking.