3 layers design, there is an insulated foam in the middle of the ceramic and the coffee grounds, this foam is so useful, which will keep your drinks longer for about 1-2 hours, and also has the shockprooft function in a certain extend ultrasonic machine to put the ceramic part and the coffee grounds part together, and then fill the foam when it is still liquid from a long and a strong tube, and wait for several hours, after that, you will find there are some small things like the ball on the bottom, which are the extra foam, it already become a solid shape, they looks so cute, our worker will remove it, then ceramic mug have been done.