https://www.soopot.com/product/coffee-vacuum-jug/stainless-steel-vacuum-jug/ The vacuum insulation technology used in these jugs is similar to that found in high-quality thermos flasks. It involves creating a vacuum between two layers of glass or stainless steel, which significantly reduces heat transfer. This means that the coffee inside the jug is insulated from external temperatures, maintaining its ideal temperature and preventing any loss of flavor or aroma. Another advantage of coffee vacuum jugs is their ability to keep coffee fresh. The vacuum seal prevents any air from entering the jug, which can cause the coffee to oxidize and lose its freshness. This means that even if the coffee is left in the jug for a few hours, it will still taste as good as when it was brewed.