This stainless steel tumbler can rapidly chill beverages to below freezing. Simply pour your drink into the body of the tumbler, which has been frozen in the freezer, and the temperature of your drink will plummet. Even room-temperature drinks become ice-cold when using the freezer-chilled tumbler! When pouring a drink straight from the refrigerator into the freezer-chilled tumbler, it can chill to below freezing in as little as 30 seconds, and maintain that coldness. Leaving a drink in the tumbler for too long will cause it to turn into a slushy. There is some evidence of use. Please consider this a used item.