Metal is an uncommon material for making tobacco pipes, but they are not unknown. The most common form of metal pipe is a pipe with a stem and shank made of aluminum or fimo, which serves as a heat sink by absorbing and dissipating heat. Mouthpieces are made of vulcanite, Lucite, or rubber. The bowls are removable and usually require a screen. They are made of varying materials to allow the smoker to try different characteristics or to dedicate particular bowls for particular tobaccos. The typical metal pipe may also come with a snuff cover similar to the attached sliding covers seen in wooden pipes. The cover screws into the top of a Metal pipe and allows the user to not only travel with a packed pipe but snuff out their tobacco by simply covering the bowl. Some snuff covers also have a light hole in which the tobacco user can smoke through making windy days or an occasional puff simple and accessible.