Universal Hanging Box Bottom File Pockets, 11 Point Stock, Letter, Standard Green, 10/BoxExpandable box bottom files are great for bulky files and catalogs. Enclosed sides with reinforced gussets. 11 pt. stock. Acid-free. Hanging File Folder Type: Box Bottom with Sides; Size: Letter; Expansion: 3 1/2"; Material(s): 11 Pt. Stock.