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 ...
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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[citation needed]. The binders themselves are typically made from plastic with metal rings. Early designs were patented during the early 1890s to the early 1900s.