50 pack 10" x 21" Brodart Just-A-Fold III Archival Book Covers - adjustable, clear mylar pH neutral PVA Adhesive and Chemically stable 1.5 mil thickness polyester Super Clear allows DJ Brilliance to show through and Prevents books from sticking together on the shelves Bottom Loading - Allows flexibility with different size book jackets. Can be folded several inches smaller than stated size Non-printed paper backing with perforated folding lines for ease in fitting and added protection