This brass replacement rod measures 19-11/16" long and 1/4" in diameter, designed for use with the Eisco Labs Linear Expansion Apparatus (PH0371). The rod is used to demonstrate thermal linear expansion — the change in length of a solid material as its temperature changes. Brass has a well-documented coefficient of linear expansion, making it a standard material for thermal expansion experiments. The raw brass rod can also be used for general hobbyist, craftsman, and metalworking applications.