Colorful when hot. We all know to drink with caution when the contents may be hot, but how do we know when it's too hot? These tumblers don't just look smart, they're designed to change color when hot liquid is poured in. Once the color disappears, you know your hot drink has cooled off. Plus, this double-wall thermal tumbler has an easy open and close switch and 360 degree drinking surface so you no longer have to search for the right place from which to sip! From Prepology(R) Kitchenware.