Which stainless steel thermos is the best?

For thermos flasks, 316 stainless steel is better. Both 304 and 316 stainless steel are food-grade stainless steels and possess certain safety properties, but 316 stainless steel has superior corrosion resistance and high-temperature resistance compared to 304 stainless steel.

 

304 is the most common type of stainless steel; many kettles and reputable tea filters are made of this material. 304 stainless steel has a density of 7.93 g/cm³, can withstand temperatures up to 800℃, and is widely used in the food and medical industries. It is known as food-grade stainless steel, therefore, 304 stainless steel has excellent safety properties.