Features: pour 100 degree hot water into the cup, shake the cup around 1 minute, and the temperature will change into 55 degree at once!  It also can keep warm for around 3 hours if the water is not drunk up. After you drink up the 1st cup of water, if pour the 2nd cup of cool water with interval of 1 minute, shake it around 1 minute, will also change into 55 degrees. If pour the 2nd  cup of hot water with interval of 1 hour, shake it around 1 minute,will change into 55 degrees. Yes, it is so magic!