Partition folder: Pocket Binder For Sheet Music Size A4 File Display Black Music Sheet Black, Used to store sheet music, documents, etc. Material: The inner pockets are anti-slip and transparent with high quality polypropylene (PP). The spiral binding allows the folder to open at a 180 degree angle for flat sheet music. Waterproof and thick pockets: the interior pockets are anti-slip and transparent, and the concave-convex technology can reduce reflected light and ensure your sheet music won't get wet when practicing. Perfect for: Suitable for daily filing and document storage of A4 and below A4 size, widely used in office, school and home, works equally well on piano, organ and performance synthesizer. Easy to use: you can insert choir and piano sheet music and other papers, standard display book, easy to insert and extract sheet music or files.