The Western futon is based on the Japanese original, with several major differences. It is almost always placed on a configurable wood or metal frame for dual use as a bed and a chair or couch. Typically, the frame folds in the middle, allowing the futon to be used as a couch, and flattens for use as a bed. It is usually filled with foam as well as batting, often in several layers, and is often much thicker and larger than Japanese futons, resembling a traditional mattress in size. Western-style futons are an alternative to a bed or other furniture, and are often sold in sets that include the mattress and frame. Futons normally feature a removable and replaceable cover in a variety of colours to match evolving modern decorating tastes. Western Futon mattress fillings vary from the economical offcut pieces of foam, to the higher quality eco-friendly natural fillings of felt and wool.