The unique Vacuum Isolated Copper Coating technology keeps the FLSK thermos bottle's beverages cold for up to 24 hours and hot for up to 18 hours. Between the stainless steel layers is a vacuum layer that prevents heat or cold from escaping, as it does not conduct like air. Additionally, an extra copper coating on the stainless steel ensures temperature retention. The perfect temperature - always and everywhere. The insulated bottle combines high technical standards with perfect design, making it a highly functional and visually appealing drinking bottle. The FLSK thermos bottle is lightweight, handy, and available in three different sizes. The lid is completely leak-proof – no more spills in the past. Furthermore, the insulated bottle is carbonated beverage safe, taste-neutral, and completely BPA-free and environmentally sustainable. The high-quality workmanship from rust-resistant and taste-neutral type 304 stainless steel ensures that your new FLSK becomes a long-lasting, reliable companion that you won't want to be without.