Mugs are receptacles usually used for drinking hot beverages. The cylindrical vessels are larger than both traditional tea cups and coffee cups, generally with a capacity of 350 millilitres. The design of the mug is geared towards insulation, so as to help to conserve the heat of a hot drink. The cups are comparatively thick, compared to other drinking vessels, and are usually made of materials with insulative properties, such as china and porcelain. The bottom of a mug is concave or made with an additional rim, both of which help to minimise the heat lost through surface contact. Mugs are fitted with a handle to ensures they can be held, even when the main body is hot.
A travel mug or thermos flask is fitted with a lid to prevent the spillage of hot liquids. The design of these mugs also helps to maintain the heat of the liquid inside for an extended period of time. Novelty mugs, such as personalised gifts mugs, offer people the chance to have a personalised slogan or image printed onto a mug, while trick-rigged puzzle mugs add an element of confusion to the drinking process. Thermochromic mugs change appearance when heated, often to reveal a hidden image when filled with a hot liquid. A shaving mug, also known as a scuttle, is not used for drinking. Developed in the 19th century, these mugs are instead intended to be used when wet shaving, and are designed to hold hot water and a bar of soap.