Sheet Music Folder: Used to store sheet music, documents, etc., sheet music folder, clef, A4 size paper with 30 slots. Material: The inner bags are non-slip and transparent with high-quality polypropylene (PP). The spiral binding allows the binder to be opened at a 180 degree angle for flat sheet music. Waterproof and Thick Pockets: The inner pockets are non-slip and transparent, and the concave-convex technology can reduce the reflected light to ensure that your clef doesn't get wet when you practice. Perfect for: Suitable for daily filing and storage of A4 size and less than A4 documents, widely used in office, school and home. Works equally well on piano, organ or performance synthesizer. Easy operation: choir and piano sheet music and other papers can be inserted. A standard display book that can be easily inserted into and removed from sheet music or files.