Thermoses with stainless steel flask

 

— the most popular modern material for flasks. Stainless steel is highly durable and reliable, it is these flasks that you should choose if you plan to use the thermos in extreme conditions (for example, on a mountain hike). However the steel walls themselves hold heat poorly, but this feature is compensated by the use of other methods of thermal insulation. Another disadvantage is the tendency to oxidize, due to which the contents may acquire an unpleasant odour and taste; however, in fact this moment is not critical, it becomes noticeable only in rather specific situations (for example, when using a thermos for some types of tea).