These are JK brand stainless steel vacuum flasks, often marketed as leisure sports bottles.Material: The bottles are constructed with a premium SUS 316 stainless steel interior for durability and corrosion resistance.Insulation: They utilize double-wall vacuum insulation to keep beverages hot or cold.Features: Available in capacities such as 750ml and 1000ml, they feature a leak-proof design and a built-in cup.