Montbell Stainless Steel Mug Set of 2 Double-walled construction with excellent insulation and cooling properties. It excels in heat retention (heat storage), making it difficult to cool down once warmed, and can keep your warm drinks at the "perfect drinking temperature" for a long time. It is highly durable and sturdy, allowing for repeated use in outdoor settings such as camping. It is also characterized by its resistance to condensation when filled with cold items and its outer surface remaining cool when filled with hot items.