Straight razors consist of a blade and a pair of handles called scales. The whole is usually held together by a pin. The blade is made from a type of carbon or stainless steel treated in various ways depending on the manufacturer (and model). The scales can be made from a wide variety of materials. The most common are celluloid (and similar), wood and horn. Other materials will work as well, such as metal, but scales that are too heavy or too light relative to the weight of the blade will result in a bad balance and a more difficult shave.