Coffee mugs are made of many different materials, such as porcelain, stainless steel, plastic, and glass. You can find any shapes and sizes to fit your needs.\r\n\r\nPorcelain coffee mugs hold heat very well and they are usually beautifully decorated.\r\n\r\nStainless steel and plastic are used together quite often, for example a have a s/s outer cup lined with plastic break-resistant. They are break-resistant and they trap heat even longer than porcelain coffee mugs. I often use them as a traveling cup.