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 you don&';t have to worry about burning your hand while holding your mug.