Built-in tabs are preattached -- just lift and label. Polylaminate is reinforced across the top edge and bottom fold for superior durability. Flat-bottom has a reinforcing insert for extra strength to handle thick documents, presentations, catalogs or manuals. Write directly on the tabs or use the included sticker labels.Package Includes: (1) Sheet of 20 Printable Labels; (20) Reinforcing Pressboard File-Box-Bottom Inserts