Brass models are scale models typically of railroad equipment, bridges and occasionally of buildings, made from brass or similar alloys. Although die-cast or plastic models have made considerable advances in late 1990s and continue to improve, brass models offer finer details. Brass models, considered to be collector's pieces and museum quality finish, are often used for display purposes rather than model railroad operations. However, these can be made fully operational and many railroaders do use them on their model railroads. They are generally considerably more expensive than other types of models due to limited production quantities and the "handmade" nature of the product itself.