Apacity: Sets commonly feature containers in multiple sizes, such as 420ml and 550ml, allowing for various meal combinations.Material: The containers are typically made with a 304 or 316 stainless steel inner liner for heat preservation and a durable PP plastic exterior.Insulation: The bag itself is often lined with aluminum foil and features an interlayer (such as PU foam) to maintain temperatures for roughly 2.5 to 3 hours.