Ring binders (loose leaf binders, looseleaf binders, or sometimes called files in Britain) are large folders that contain file folders or hole punched papers (called loose leaves). These binders come in various sizes and can accommodate an array of paper sizes. These are held in the binder by circular or D-shaped retainers, onto which the contents are threaded. In North America, the rings themselves come in a variety of sizes, including 0.5, 1, 1.5, and 2 inches (13, 25, 38, and 51 mm), though other sizes are also available. The rings may be secured by lever arch mechanisms or other securing systems, or may be spring-loaded. The binders themselves are typically made from plastic with metal rings. Early designs were patented during the early 1890s to the early 1900s.