5 Brodart Just-A-Fold III Archival Book Jacket Covers - Mini Popular Pack - Clear, Mylar, Adjustable Super Clear allows DJ Brilliance to show through and Prevents books from sticking together on the shelves pH neutral PVA Adhesive and Chemically stable 1.5 mil thickness polyester mylar sheets Bottom Loading - Allows flexibility with different size book jackets. Can be folded several inches smaller than stated size Paper backing with perforated folding lines for ease in fitting and added protection