Refractory materials are a type of heat-resistant material used for a variety of high-temperature applications, such as lining furnaces, kilns, and other heat-treatment units. Refractory bricks are the most common type of refractory material, and are made from a variety of clay-based materials and other minerals. Castable refractory is a type of refractory material that can be mixed with water and cast into desired shapes. It is most commonly used in kilns and furnaces which require specific shapes or contours to ensure efficient heat transfer.