The double-wall vacuum-insulated walls give you a worry-free mind knowing your beverages are kept icy cold or piping hot for hours. Made of lightweight 18/8 food-grade stainless steel that is non-leaching and will not retain taste or odor. The double-wall technology prevents condensation on the outside for those hot sunny days while keeping the heat within the inner wall so every hot chocolate is as warm as it was coming off the stove.