There is a kake-buton (comforter) cover and a shiki-buton (mattress) cover. The kake-buton cover is to wrap the whole area of a kake-buton to prevent it from getting dirty. There are several types: the one with a side zipper (you can put a futon in and out through the opening on the side of the cover), the one with side strings (close a cover with strings), the one with side snap fasteners (close a cover with snap fasteners), the one with the open window (the cover has the open window on its central area and the fabric motifs of the futon look like a picture in a frame), and the one with the mesh-covered window. About the shiki-buton covers, there are several types: a bag-like one, the flat sheets and the fitted sheets.