Fashioned from food grade substances, each Joulie consists of a stainless-steel shell filled with a ‘special phase change material’ which absorbs the heat of your coffee before releasing it at the right moment. They’re only 50 percent heavier than ice cubes the same size which means they sink to the bottom of your mug so you don’t need to worry about knocking out your front teeth.
At US$95 they’re quite expensive but they’ll also save you money on wasted coffee gone cold. For that price you actually get five shells as well as a thermos, which combined with the Joulies, should power your coffee till Christmas. We just think they’ve missed a trick by not roping in Ali G to help advertise their Julies.