These books are made with a lighter weight 150 gsm (40 lb.) card stock cover. They are filled with high quality 80 gsm (20 lb.) paper, and are chlorine-free. These books are not available with onion skin page separators.Pack of 25 books. For vocabulary. Packing unit: 25 books, 36 pages, portrait format, 16x21 cm (6.3x8.27 inch), lined.